64mm Or 69mm Valves For 139QMB GY6 50 Scooter Engines

[@wimpraet5161]

Really super well explained with absolutely nothing forgotten in the difference between the two cylinder heads and their rocker arms. Nothing extra can be added to this extensive tutorial. I have both lying and everything is correct to the last detail.

[@Spitfireseven]

DUDE!! You are amazing! You did the most sensational job of explaining this subject. The fact that you cut and painted the heads alone is almost unbelievable. Now I know to look for ported heads for better performance. There isn't anybody that could do a better job than what you did here. Thanks again!

[@thomasdsmith7678]

Bought a full 90cc big bore kit that came with a new head and 69mm valves. It came with replacement rockers (different ratio) to use on the cam from the old 64mm head. Thanks for the channel. I buy abandon/weathered GY6 scooters and rebuild them.

[@-TD227]

be careful with 90cc and above because they can overheat

[@altimategamer12]

Its not a 90cc the highest a gy6 can go bore wise is 52mm 88cc and anything bigger than 72cc will not only overheat but overstress the cranknand bearings tonthe point that the kit wont last any longer than 3000 moles or so

[@garthkey]

I have a scooter and when I hit full throttle on the stock engine the handle bars feel like they are slanted

[@Donbscooters757]

​@@altimategamer12so going with a 50 to 100 cc Big bor kit I shouldn't do it and with what you stated I thought about putting a oil cooler on the motor after I did the Big bor kit would that help the overheating issue and help the motor to have a longer life if you can reply I would appreciate it thanks

[@kylandaminick13]

thanks for the awesome video man! you are essential to many people learning

[@adolphjanssen6580]

Very good and precise info and a pleasure to watch. Very easy to understand

[@leodano2947]

Great video as I was wondering the same thing. Basically there is no performance gain, but the 69mm head allows more room for porting.

[@donaldpulliam9153]

There is always more room for porting when you're 69ing 🫢🤭🫠🤣

[@sajmirbekteshi9113]

BRO KEEP TEACHING USSS YOU ARE THE BEST MUCH LOVE FROM ALBANIA 🇦🇱🇦🇱

[@DeadLetterOpener]

Awesome video mate! I was impressed by your investigative motivation, dissecting cylinder heads is going above and beyond. :D Really enjoy your videos man, looking forward to the next one.

[@49ccscoot]

Thank you!

[@Donbscooters757]

Your the best dude I've said It before ill say again i can and do learn alot by watching ur videos sir i appreciate you and what you do for these videos

[@pierdolio]

Now that's an eye opener! Great job.

[@robertbell1804]

This video really helped me out my cylinder head on my moped is bad I had to replace it.I didn't know what size my old one was so I got a 64 mm now I know my old one is is 69 mm so now I have to order 64 mm rocker arms.

[@paulbudford]

Very interesting. Every day learning something new.

[@irocss85]

Super interesting. I did always assume it was the valve size, but ofcourse that's way too big. Lol. Just never really looked at it. But, I'm so glad you showed the cutaway because I have both, and want to port a head for a performance build.

[@1blaq1]

Valve heads just got easier lol great video

[@49ccscoot]

Thanks!

[@jakespeed9419]

I am so thankful for this video!!! Great job so informative!!!!

[@spidervenom3341]

I have a 49cc Linhai Joc I upgraded the engine with a 50mm bbk, and after about a 100 miles my intake inner springs broke,have new ones ordered and now I found this video telling me that both heads use the same spring sets..lol..looks like I got some extra spring in case it happens again..thanks for the info...

[@wilfredgarcia9564]

nice job man!! very in depth. thank you.

[@Tony13754]

You do a Great job explaining the work ! Thank you ! You've been a GREAT Help to me 👍

[@49ccscoot]

Thanks. Glad the vids are of use.

[@igorcossetto4779]

Very best explanation, Thanks🏆👋!

[@davidcoates4852]

Excellent video 👏. Solved my problem. Bought a non-runner with no compression. Previous owner installed a BBK and it wouldn't start. 64mm rockers on 69mm valves. Valves would not close even with tappets removed. Thanks 🔧👍

[@Donbscooters757]

Was that because the valves were the wrong ones . They were the shorter ones ?

[@davidcoates4852]

@Donbscooters757 The valve was too long, the piston hit it at top dead centre.

[@JohnCalebWarren]

Excellent Video man! Absolutely Excellent! 👍👍

[@jason187smoot8]

Thanks a lot bro you are a good dude for sharing your knowledge with us.. Saved me a lot of $$

[@locotrucker46]

Thanks for posting this video. It was very informative and very helpful.

[@TheShock37]

Big Thanks to You! Very easy to understand. Hello from rus)

[@ClosedLoopMusic]

Is there a way to tell what valve size with out disassemble the motor ? Like by the vin number or something ?

[@kreepingdeth198]

If you would've watched the video, you'd know.

[@walternqn]

Que buena informacion! Muchas gracias! 😃👍🇦🇷

[@glowskulls100]

Thank you for that been trying to work out which one I had as one bbk states only for 64mm head. Milly

[@Scooter-chinois-4t]

Hello how much does it take to set the valve game? What size of jet should you install in the carburetor? What weight of rollers do you recommend for the drive? For the clutch that advise me? Thank you for your advice

[@49ccscoot]

Valve adjustment : kzbin.info/www/bejne/qWGuXqyqrs-CfMk The carburetor should be tuned. 1 jet size doesn't fit all : kzbin.info/www/bejne/gWbNaZp-nJqeg8U www.49ccscoot.com/faq/carbtune.html Again with the rollers, I recommend tuning. 5g sliders are pretty common for a stock 139QMB upgrade though. I prefer sliders over rollers. : kzbin.info/www/bejne/gWbNaZp-nJqeg8U Get a few sets of springs for the clutch and see which work best. I know these aren't the answers most want, but IMO anyone that says X jet, X rollers, or X springs are the best for all haven't done enough tuning. Many will be happy with generalized guesses, but also many will find lackluster performance.

[@Scooter-chinois-4t]

Thank you very much for your reply and advise fast.

[@49ccscoot]

You're welcome. Good luck with your project.

[@yendor29]

What head would be best with an 80cc kit?

[@49ccscoot]

Whatever matches what you have is the easiest. Then you don't have to worry about mismatching valve lengths.

[@ruben05chevy_sanantonio22]

So I got the 52.44mm big bore kit from Naraku the valve springs are seated in a galley so that head will use 64 mm rocker arms right

[@danieleriksson9249]

Great video! I bought a Viarelli matador and hade to buy a new cylinder head. I incorrectly bought a head with 64 mm valves and original rocker is for 69 mm. When I contacted racing planet they said that I could put the nut for the adjustment screw under the arm instead. Could that work. Any one tried this? Thanks.

[@mbrofc]

Excellent, extremely informative.

[@RachidEd]

Thanks for your informative video. I recently upgraded my gy6 scooter from 80cc to 100 cc cylinder. The mechanic that worked on it kept the 64mm cylinder head. He handed me two 64 mm valves with ol seals told me he replaced them. However I couldn’t notice any change even lost power at accelerations. I began watching videos when I stumbled upon yours. I suspected there is an issue with valve clearance. I checked myself the intake was no lash at all. I fixed it to 0.08 mm whereas the exhaust was too loose 0.15 mm. I fixed it to 0.10 mm. The issue is I don't know whether I have 69mm valves on this 64 mm cylinder head. The tappet nut in the exhaust screws just fine whereas in the exhaust the nut screws out as in your video. I guess there is a problem with tha angle. Even though the scooter runs great except for some loss of power from now and then and some spluttering from the exhaust. What would you recommed? Thanks again for your great tutorials.

[@49ccscoot]

Number one would be find a new mechanic. I'd try to take a close look at how the valves interact with the rockers. They should meet up flat against each other. If they don't you may have a mismatch or other problem.

[@jimm4260]

Thanks for this video! very helpful

[@jamest.5001]

With a long valve there is less valve guide in the port blocking flow, and the port can be raised when porting, to gain performance, you can gain some performance on either, by adding an additional shim under the springs, only one extra. So 2shims, you can go with 3shims, but you must check clearance, the springs can bind, but only if there is signs of valve float. More pressure only eats power! You just need enough pressure to control the valves, if it was me, I'd make the valves even longer, 74mm, and make the ports even higher in the head, nearly 15mm on the inside, to get a better shot at the valve, and spread the valves out from each other. But they would not work with a stock bore, 47mm and up, maybe go 4x -18-19-20mm exhaust valves, and 22-23mm intake, valves, with dual cams, with rocker followers, the intake side cam working the exhaust, and vice versa! Making it easy to put the sparkplug in the center, allowing two cylinder engines to be built, or more! A gy6-85 4cylinder haha!! 81-83cc x4 If I had a mill and lathe I'd build a 2cylinder with 52.4 bores, and big valve heads, with a8-a9 cams, and single 30mm carb if I even had a good drill press, and a welder I could weld aluminum with, .maybe even build a stroker crank! Get about 100cc per cyl from it, I think it would perform better than a gy6 150 big bore, nearly 200 cc, being it fires two cylinders,

[@49ccscoot]

If you could just take 1 cylinder off of a sportbike and graft that to the CVT...

[@SiberIndustries]

Nice video. Thank You :) When upgrading a 50cc with a big bore kit, does it matter if one gets the 64mm kit or the 69mm kit? Other than porting, is there an advantage/disadvantage to either such as more/less power, speed, acceleration, fuel use, wear, noise, vibration, etc? What's the purpose of having both on the market? Or is it just basically a longer/shorter version for no reason.

[@49ccscoot]

+Siber Industries The only reason it matters when you get a BBK is if you'll need different rocker arms. As long as you have the right rocker arms for the head that you choose with the BBK, you'll be fine. I don't really know how the aftermarket heads are setup. Unless you are willing to get into a lot of port work, you probably wouldn't notice much difference from 64mm to 69mm. I'm not really sure why there are 2 versions. It could be that 69mm is intended to be an improved head or for all I know it could be that they have 69mm long valves around from some other application and decided to use them. Sorry, but I just don't know.

[@twinflametaurus]

It only matters because that's the size that matches the top half of the engine block. Really , if your engine is new when you do the bbk, You can usually save money and just reinstall your original top half of the engine assembly onto the engine. Just be careful , if also replacing cam , that might need new custom top half of engine.

[@sajmirbekteshi9113]

Can we add watercooling to the 4t engine

[@49ccscoot]

There's no reason that it couldn't be done, but I don't know if there are parts for the 139QMB. There is definitely stuff to make liquid cooled GY6 150cc+. Maybe some research into other stock liquid cooled 49cc would allow you to find parts to be adapted.

[@birolc.9112]

Will it cause problems if I use 50mm cylinder and 52mm cylinder head? To reduce the compression ratio

[@49ccscoot]

You'd be better off with a matching bore diameter or smaller bore diameter and proper combustion chamber size. The sort of mushroom shape up there won't be good for performance and could encourage detonation.

[@JonahNAloha]

On the 69mm head, does the valve have a longer stroke? Or is it the same equivalent stroke as the 64mm?

[@49ccscoot]

The valve itself is just longer AFAIK. I have not measured rocker ratio to tell you if there's any difference there.

[@JonahNAloha]

As I see it, it probably would work the same if it’s same length. As the stroke is still the same with the 64mm and 69mm.

[@Smodlee]

Which one makes more compression? I am looking to get the 52.4mm BBK but don’t know what head to use for more compression the 64mm or the 69mm

[@49ccscoot]

Shouldn't matter. That's about combustion chamber size, deck height, piston design...

[@ArcadeCabNBud]

that was very interesting to watch mate, appreciate your effort, thanks

[@johnfloyd2551]

Some people confuse valve height with valve size when refferring to a "big valve head" i wanna know about the big valve head, are these better? Does the larger valve diameter make a difference?

[@49ccscoot]

It can help, but the worst part is that sometimes they make the combustion chamber so big with big valve heads (also generally intended for big bores) that the compression change seems to kind of make it even out. This is what people on my forum are reporting.

[@Timo-Epis]

What happends if the valves are not 100% alligned with the rockers? Will it still work but do you loose performance?

[@racerx757]

Awesome Job its just what I wanted to know thanks, just wondering could you tell if it looked like one head would Flow better then the other ?

[@49ccscoot]

Daniel Lee I'd guess they'd be similar, though it appears there's more potential with the 69mm valved head.

[@jefferyyoung5401]

do you need a different cam with different length valves?

[@49ccscoot]

Same cam.

[@rallyscoot]

@@49ccscoot Also same cam with 4 valve head?

[@49ccscoot]

@@rallyscoot I haven't seen a 4V 139QMB that I recall. They are out there for the 150cc GY6. I know that at least some of those use a split rocker style, so one lobe can actuate 2 valves. That style may be able to use standard cam designs, but you would need to check when you choose a 4V head.

[@derrickleger9558]

Hi i watched the video twice, and must have missed the part i was looking for. I am looking to buy a bike with a 139QMB engine, and I am planning to get a 80cc big bore kit for it. Is that engine 64mm or 69mm. i know u mentioned that sometimes the P in the engine name means 69mm but then you said not always. Please help, thanks.

[@49ccscoot]

It could be either one. Definitely all P engines aren't a certain valve length, and all non-P engines aren't either. That would make it too easy on us I guess.

[@kalani1963]

You'd have to disassemble to be absolutely sure. I have a BN139QMB motor with 69mm valves

[@CodyJv]

What would be the valve clearance for a big bore from a 49cc? I acquired a scooter and the seller said it has a big bore kit, I did get the spare cylinder, rocket, head. I assume it was done right.

[@49ccscoot]

I set most to 0.002-0.003". 0.005" would be about the max.

[@CodyJv]

Exhaust and intake ? Btdc ? Or tdc

[@jamescruze6443]

I need your help badly....i just need to know what type/ size/ matching parts to buy!!?? Valve-intake-oversize carb-air filter-etc

[@Smedleydog1]

I have noticed that the 69mm valve heads have the port for the EGR drilled and the 64mm heads don't. I don't know if that is true of all 69mm & 64mm heads. Also it would appear on the 64mm, the head intake & exhasut ports are already opened up a little more than on the 69mm heads. It makes you think the 64mm heads would flow better. Fantastic video!

[@49ccscoot]

There are 64mm and 69mm emissions and non-emissions heads available. Thanks.

[@JonahNAloha]

What about bn139qmb motor. Are those motors any good?

[@49ccscoot]

Same thing AFAIK. Some manufacturers use a little different lettering. BN is made by Znen.

[@omniaparatus1890]

Do you recommend high lift rockers if doing a bigger head?

[@49ccscoot]

Most just use whatever works with their current setup. I'm not really sure if aftermarket heads have the same layout as stock heads. If they do, the 69mm setup would be a bit better.

[@omniaparatus1890]

@@49ccscoot thanks for the info. Look forward to more uploads. You have taught me loads of things so far

[@Zodiark-]

Such a good channel...top quality material 🖒🖒🖒

[@49ccscoot]

Thanks!

[@miguel360kmc]

My buddies Q6 icebear trike we did a 50mm bbk bolt on build.. And when i was called in to do timing and 69mm head i could not change out rocker arms the pins would NOT come out (only 40miles on bike) and 1 of the arms (i think intake) was very tight and did not move as freely as I believe it should up and down.. I told him he wanted it on so we sent it.. Now it seems like its over reviving hitting way high RPMs before getting to speed. Could that rocker arm be the reason? If not what issues could pop up due to thight arm thight pins?

[@brandonhubert3215]

I know this is a random question but what do you set your valve cap on a 100cc bar kit for 50cc engine

[@49ccscoot]

Most of the time I do 0.002"in/0.003"ex. They don't need more clearance just because the bore is bigger.

[@jamest.5001]

So you can port the 69 mm heads a bit more, without running into the spring pocket! I had a tiny issue with this, I'm looking into larger valves!

[@BlaserAndDesert]

Nice video! So i can mont. any 100cc big Bore made for the gy6 engine. Even If you have the 64 or the 69? Its just the head thats the diffrent? Its that right?

[@49ccscoot]

The cylinder and piston kit should not be different.

[@BlaserAndDesert]

Thanks! :)

[@vernstires7186]

GREAT VIDEO. I only have one question. Will the valve cover for a 64mm valves fit a 69mm setup?

[@49ccscoot]

It should.

[@dubeights]

Does a 69mm valve head give you any performance increase? or what would be the point of going from a 64mm to 69mm setup?

[@dubeights]

Ignore this post, I'm on some forum right now reading your post responding to a similar question lol

[@jerodoque]

Great video! Can I ask how you cut the head in half? What tool/s did you use? Any info would be appreciated

[@49ccscoot]

Just a hacksaw IIRC. Then I sanded it on sandpaper over glass to smooth it out on the cut sides.

[@jerodoque]

Thanks for the info!

[@WillB-lv1xg]

Is there a 4 valve head for the 49cc or is it possible?

[@49ccscoot]

If you google "4 valve 139QMB" you should see a 4V head. They're out there, but I don't know anything about them.

[@Manwichman]

I have a hose coming off the front of my engine?... It's in front of my carburetor if I open the little panel in front of my seat. It is not connected to anything and I can tell it used to be clamped on something as the hose end is widened and I see indents where the clamp was, what is that supposed to be connected to?

[@49ccscoot]

Is it an air filter/leading to an airbox? If so, the carb would be open (no filtration) till you get it hooked back up.

[@Manwichman]

@@49ccscoot it was leading to the air box...I put a uni air filter, did an emission delete and put a little mini air filter on the end of that hose. Hope it works and it seems fine

[@Donbscooters757]

So im doing a bbk soon and i was going to use the stock original head with the big bore jug that im going to order because mist thst i have seen that can be ordered don't come with a head just a jug and piston well bim looking at the cheapy bbk to be honest

[@Yakplanet_tv]

For 64mm valves. What adjustments do I need to tune to. I cant fine any right answer to adjust it To.

[@49ccscoot]

I use 0.002" intake and 0.003" exhaust on 64 or 69mm valved 139QMBs in most cases.

[@rallyscoot]

@@49ccscoot hot or cold?

[@49ccscoot]

@@rallyscoot Cold.

[@marineboy4181]

And hey bro I keep getting the wrong rocker arms what miligrams do I need for a GY6 90cc Big Bore Kit from Taiwan? You're always there for us man I'm going to need you again bro sorry. I keep getting the wrong rocker arms now I know you know which one I need if you can send me the link as well I appreciate it bro.

[@49ccscoot]

It depends on your engine. There should only be 2 types. 64 and 69. Order whichever you don't have now if it's wrong.

[@marineboy4181]

@@49ccscoot well I have a 93 CC and it's a 139 GY6 of course and it's a 4-stroke

[@marineboy4181]

@@49ccscoot and like I said before I have a Taiwanese 93 Big Bore Kit from Rolling Ridge bro

[@49ccscoot]

@@marineboy4181 Right. Did you watch this video though? The 139QMB can have either valve size, so you need to check as shown.

[@marineboy4181]

@@49ccscoot and sorry bro yes I watch the video sorry for the late reply I had to get up to go to work. I talk to the person that I ordered the 90cc Big Bore Kit from and he said that I needed a 64 so I ordered it 64 mm not 69

[@dejanbarjaktarovic6555]

thanks

[@mannymoejack8181]

this is a great video and thank you for posting it. my question is what is the advantage of one over the other. if they are the same diameter but different length is there a difference in the way the motor runs. more air flow with the 69mm valves? I'm not doing any porting but I already have the 64mm valve head and 100cc bbk. thanks again.

[@49ccscoot]

I would suspect that real world difference would be very minimal. Either one could have advantages and disadvantages. For most of us that don't need to be incredibly competitive, either one should be fine.

[@ErmaTheKitteh]

How tricky with all just the different lengths.. ugh! Also i wounder, if i change to 69/64 will i have to change the timing chain? alongst with talking about timing chains.. apperantly to my service schedule on my scooters manual, i shall replace the timing chain at 4000km (about 2500miles) and the bike got about 1900miles on it.. do i really have to replace the timing belt that early? concidering its normally an item in cars/motorcycles that never need to be replaced more or less.. and doing so, is it hard, like does one have to split the engine or something similar?

[@49ccscoot]

The timing chain should be the same because you aren't changing the distance from the cam to crank or the size of the cam gear. Basically your valves are just raised 5mm. The head, guides, valves, and rockers are all specific to each style (64or69mm). Otherwise swaps shouldn't be an issue. The timing chain should be alright at 2500 miles. If you don't see an issue with it, like it's really loose, you should be fine. Even if it's loose, first I'd check the tensioner.

[@ErmaTheKitteh]

***** Alright, thanks man! :)

[@sotopr7]

If i put a 100cc bore kit how come some come just the cylinder andnpiston and some come with head wich should i use

[@49ccscoot]

They can fulfill different needs/wants for engine building. Not a good idea to use a "100cc" kit with a stock head, so if you don't have a suitable head then you should get a kit that includes everything.

[@bencollins2297]

What valves should I habe on a 2017 gy6 qmb139 factory tokens they come with 64s just wanna make sure tho

[@integra91ah]

so essentially if I were to buy a bbk and it came with the new head and valves were already in it would it matter ? ..

[@49ccscoot]

+2SHAYNEZ Unless it includes rocker arms too, yes. Rockers must match the valve type.

[@integra91ah]

+90GTVert OK cool. so if I but a bbk and come with a assembled head I'm hood to go then.. Thanks for messaging me back.

[@dedeabsrn8044]

intake: how many mm is the valve pitch? Exhaust: how many mm is the valve spacing? for best performance?

[@servicetech00211]

Great detailed video!!

[@JonahNAloha]

What if I was to put a 64mm valve on a 69mm head? Would it run the same?

[@49ccscoot]

I'm not sure if they are interchangeable because of the way the head is cast/machined to accept the different valve lengths. It would probably throw off the specs like seat pressure and may even lead to coil bind. Never tried it.

[@integra91ah]

so how do you feel about the talk about the 1p39qmb being a sleeper 64cc..? true or naw

[@49ccscoot]

+2SHAYNEZ False. There were some. Seems to be very uncommon in more recent years. The P does not mean it's a 63cc.

[@integra91ah]

+90GTVert thanks for the reply. I had mixed feelings about it and didn't believe it either.

[@integra91ah]

+90GTVert also when doing a pair system removal does the hose on the valve cover go to a canister ? or can you hook it up to a air filter ?

[@49ccscoot]

+2SHAYNEZ 49ccscoot.proboards.com/thread/997/crankcase-venting

[@integra91ah]

Thanks I appreciate the help

[@tjayismael9692]

do they both give different performance or is it the same

[@49ccscoot]

+tjay ismael Should be about the same. 69mm head may have more potential if you wanted to do a lot of port work.

[@tjayismael9692]

have you ever used the lightened rotor kit for the qmb139 motor. im having hard time doing the set up because the wires are lil different for my bike. n e tips on how to make that one work. or do you have any videos using the qmb139 rotor kit.

[@49ccscoot]

No sorry. I've used an NCY/Hoca small flywheel on a Minarelli, but the wiring was a direct plug in. It should be fairly simple if you have the typical 2 ign wires from the stator. You'll have one wire that's a pulse/trigger for spark that should put out roughly .5VAC when cranked over. Another will be power for the CDI and that should put out 50VAC or more. Those would head to the CDI. The others should be AC charging and lighting output and maybe a ground.

[@tjayismael9692]

i have a CPi Mako bike. jog90 crank. i was looking at the NCY/HOCA lightened flywheel but the wire connections are different. those kits comes with 2 loose plugs and 1 plug with 3wires. my bike has one big wire with only 2wires that connects to stator. any tips on how to get it to work on my bike with lighting and everything to work good.

[@49ccscoot]

IIRC mine came with an adapter, but you can contact a seller and ask.

[@RickyBish]

The part where in the cover that grabs the fan side to turn the motor over . Its like a kik gear im sure you know what im talk in about well where it sists in and spins (hooe im explaining it well enough) but the metal is cracked im thinking i can jb weld it to fix the cover that goes to my motor i feel like it will hold but im not 100% sure

[@49ccscoot]

It would be better with an actual weld or replacement. I get that those cost money. Just not sure that JB Weld will hold up.

[@kathyperry-gu2gz]

Does anyone know the exact dimensions of a set of 64 mm rocker arms

[@ryanjosef]

Im curious, from what I am seeing there are two different heads for the same engine. What is making the difference? I have a 2014 atm50-a1. Thanks

[@49ccscoot]

+Ryan Szumiesz The difference is explained in the video. If you mean why are they making them different, I'm not sure. Your TaoTao should have the 69mm valves. Mine does and anyone I recall posting about it says they have 69mm valves so I believe that to be the standard for TaoTao.

[@richardworden9747]

Can you please tell me if I put a 47mm bbk on my gy6 139qmb 50cc bike do I need a oil decompression kit ? And thanks much. Sir

[@49ccscoot]

No, you don't need that.

[@sahelgmaing601]

Hi I opened my valve cover to check on my valves and I noticed my head nuts were loose so I tightened them but a little too much and one of them put a crack on my assembly so I ordered a new one a 64mm even tho I have a 69mm I did not know until this video. But when I was installing it the cam shaft would not go in place every time I pushed the assembly down the cam would not go in place and tilt up and when I tightened it the engine did not spin is this because it’s a 64mm assembly in a 69 or did I do something wrong because I tried to push the cam back and forth and nothing worked out

[@49ccscoot]

You need the proper assembly to match what you had. Also, make this a learning experience and torque to spec when dealing with engine fasteners whenever possible. Stuff happens even then, but much less.

[@sahelgmaing601]

@@49ccscoot so basically I should get the 69mm sense my engine is 69mm right I just want to make it clear before I buy and thank you so much for your reply I will definitely tourque it to spec thank you agian

[@49ccscoot]

@@sahelgmaing601 Correct.

[@sahelgmaing601]

@@49ccscoot thank you so much you have helped me a lot have a wonderful night

[@nxgraphics]

perfect thanks brother

[@jamest.5001]

A bit of epoxy. Will fix the intake if you only have a tiny hole like I got into, but the exhaust you either weld it or scrap it!

[@kissanloikka217]

hello brother, I know this might be little ot question but: I have kymco super8 4t 50cc scooter which is in stock(only cdi unrestricted). What would happen if I installed a9 camshaft to the stock scooter? would it improve performance or just be waste of money and time? thanks.

[@nicholascorbett6655]

I have the p139qmb engine that suggests the 69. I already ordered 64. Is that a problem?

[@49ccscoot]

All P engines aren't 69mm. If you have a 69mm engine and put a 64mm head on, you can swap the rockers or whole rocker assy for one for 64mm and then it should be fine.

[@nicholascorbett6655]

@@49ccscoot as always thanks so much for your help. The original rockers from first BBC fit perfect. Used feller gauge took a few kicks and she started no problem.. ran about 6 miles around up and down fast med slow idle etc.. brought her in the garage shit her off with kill switch. Changed oil and now no start. I got compression from spark plug valve but when I start with plug exposed no spark.. I made sure cdi connections were good bc I tried the dumb orange box and 3 prong spark plug but now just doesn't want to kick. Room temp I'm at a loss

[@49ccscoot]

@@nicholascorbett6655 See if you have power from the stator. kzbin.info/www/bejne/p2qQnqVtd718ntE

[@DarkHorseModz]

So if I grab a basic 72cc BBk with 69mm head set. It should work fine on my stock setup either way correct? I plan on using my factory head as I was informed it should be fine if I keep the BBK size down. ?

[@49ccscoot]

You still need to match 64/69mm valve related components. Doesn't' matter what bore size. Stock heads may work on smaller bores and not larger because of compression, not due to valve length.

[@DarkHorseModz]

@@49ccscoot so even though I opt to run my stock head possibly I should take off the cover and take a peak to confirm valve length even though I'm not planning on changing the valves and just changing the jug part? Only ask because I see basic "jug" BBk and then full BBK with new heads and jugs. Again plan was just going 39-47cc piston size

[@49ccscoot]

@@DarkHorseModz If you're using the stock head, it doesn't' matter, but you mentioned a kit with a head too. Then it would matter.

[@cemtkeenan2750]

Does anyone know if we can install two intake valves instead of a smaller exhaust valve?

[@gianlucaorlando5471]

how do i know if rocker arms is correct for 64mm or 69mm? I threw away my original cylinder head (kymco agility 50 4t R12 2007) now I have a malossi 52mm cylinder and 52.4mm naraku v2 head with 64mm valve.

[@49ccscoot]

You should be able to look them over when installed and see if there are alignment issues. Someone can probably tell you what Kymco had stock, but I'm not sure.

[@wisebeardman7197]

Okay, so lets so I buy a big bore kit that is a 64mm kit and my scoot has 69mm heads installed. What are my options? Can you just buy some 64mm rocker arms and swap them out? I'm not exactly clear on that. I know nothing about engines, I have a small scooter project just to try and learn about mechanics myself.

[@49ccscoot]

You can get the different rocker arms and swap them, or a whole rocker assembly.

[@kalani1963]

You can use you whole 69mm head, rocker assembly included and just purchase the 80cc or 100cc piston and piston body.

[@Motoman714.]

8 ordered a 100cc big bore kit that came with a 64mm valves. Can i swap springs keepers ect

[@Motoman714.]

Oh nvm

[@49ccscoot]

Rockers or rocker assy is what you'd need to swap to make it work usually if they don't match.

[@Motoman714.]

@@49ccscoot I ended up figuring out how to make the 64 mm adjust to my rockers properly and aligned properly in it runs good only problem is is it Burns oil is that because my piston oil ring and compression ring gaps are aligned with the wrist pin?

[@49ccscoot]

@@Motoman714. Could be. There's an image here (scroll down) that shows how rings should be installed. www.49ccscoot.com/bbk.html

[@Motoman714.]

@@49ccscoot thank you

[@kaius8821]

I recently ordered a BBK, come to find out it has 64mm valves. It comes with the entire assembly, rocker arms and everything. My TaoTao came with 69mm valves, will i run into any issues during the swap? Thanks! I always love your videos, you have been a blessing over the last few months with my scoot issues!

[@kaius8821]

+Kaius Azelle Sorry if you've already answered this question, i haven't been through the comments much.

[@49ccscoot]

+Kaius Azelle As long as you have the appropriate rocker assy, you should be fine.

[@kaius8821]

Awesome! I watched another video and the guy said that if your scoot comes with 69, keep it 69...maybe his kit only came with rockers that were designed to fit 69 and that's what he was referring to, but anyway thanks!

[@49ccscoot]

You should be able to swap it around either way. The main argument I'd think for keeping 69mm is that the head appears to have more meat on it.

[@evanknight3629]

To be honest I would just put it together and visually inspect everything and then move the rockers up and down to make sure they aren’t all stiff if it looks right it’ll run

[@kathyperry-gu2gz]

I have a very specific reason for asking this question I know what a 64 mm and 69 but I need the specs for the 64 mm rocker arms I if this works like a plan do something awesome and let everyone know

[@loboicjusz]

Thaks, that's important...

[@christophercollins3143]

I have already put a big bore kit on my gy6 from 49cc to 100cc how big can I go.

[@49ccscoot]

100cc is already bigger than you can get, so that's pretty good. The last time I checked, the largest setup was about 95cc with a 44mm stroker crank and 52.4mm bore. Unfortunately a lot of sellers call their big bore kits 80 and 100cc even though they are not. 49ccscoot.proboards.com/thread/2953/displacement-torque-tables-gy6-139qmb

[@210life2]

I bought an 69mm valve head from amazing installed it onto the gy6 50 Cc and it sounds like it has no compression what so ever I also bought another one from a different website and it did the same thing what do I do

[@210life2]

Nevermind I kept watching longer into the video and u explained the rocker arm situation

[@normiswow]

Hi! I wanted to ask if you know how to straighten bent wheel disks not the rim but when theyre bent in the center it's not much but still annoying and feels like my scooter is losing power because of that. Do you have any solutions for that ?

[@49ccscoot]

Sorry, but my best advice would be to replace them. Usually can find them fairly cheap for common scoots on eBay or you can try the classifieds section on the forum at 49ccscoot.proboards.com

[@carlosmartinez-yh5ps]

can i use my stock head 64mm on my 50mm big bore kit or dose it have to be a 69mm head

[@49ccscoot]

Stock head would be OK aside from the small combustion chamber. Could create too high compression and lots of heat and/or detonation.

[@RickyBish]

Please help my issue is I have a 80cc jug and piston that I have a stock 50 head on and what I'm learning is that it has too much compression so how can I remedy this I have several other heads that on the bottom side ( combustion chamber) that are made different I need to know what to look for in the heads I have that will lower the compression in this 80cc set up I also can tell it's putting too much tension on the timing chain as well tell me please someone what to do

[@49ccscoot]

If it's low compression and putting more tension on the chain, then I'd think the cylinder is a little too tall. Could potentially have that milled down a little, but that would involve a lot of checks first and machine shop money. A head with a larger combustion chamber will lower compression, but that won't do anything for chain tension. Another option would be to try a thinner base gasket and/or head gasket.

[@RickyBish]

I have other heads with different combustion chamber smaller ones

[@RickyBish]

One more question would it be ok to ride my scooter with a partial part of the transmission are to be exposed (where the belt is located I don't have the funds to buy a new cover and I had one for a long case engine so I had to cut it in half to be able to have a working kick start

[@49ccscoot]

@@RickyBish The CVT being open is OK-ish. Plenty of people vent them. Main risk is something getting in there, but many do it. The cover being in two pieces is a more serious potential issue. The cover helps to support the case. People have snapped engines in the middle of the CVT area before when not using a cover. Not saying it's common, but it is a risk.

[@Balu0389]

Спасибо! А как распознать на вид сами коромысла ?

[@thephranc]

The 69 looks like a much better head over all. That extra meat in the head will reduce valve deflection and seat distortion at high RPM?temp. It should also make the cam slightly more stable

[@49ccscoot]

Good points. Thanks for the input.

[@thephranc]

***** Thank you for cutting heads in half.

[@jamesdiaz9581]

Can I use a A9 CAM ON 64MM VALVED HEAD

[@49ccscoot]

Sure.