Motorized Bicycle Build MS660 Cutaway Timing Video - Long Rod Explained!

When I built my Sawzilla builds! Full How to here: • MS660 Motorized Bicycl... I had talked to many Comp saw builders and got there opions on this build before I started it. I learned much info that the google search/ forum bad information crews spread and tossed that to the curb. So much bad information or half complete information. So I wanted to explain why people use a longer rod! Why that makes the build run better or the common yd100 rod that almost always blows crank bearings and snaps a skit off the piston in a pretty short time frame!
TIMING CUTAWAY VIDEOS PLAYLIST: • Timing Cutaway Videos
Yes! I realized your piston will be hanging out of your piston 04:50 oh well not changing it now lol!
I wanted to touch base on Piston ring! I showed an Extreme case of it so you can see what I mean! This the number one cause of Crank bearing failure! Repeated slamming of bottom end of the piston! Very distinct ring you hear 90% of all these builds people make cause of bad info they go to make one! yd100 rod will not work well in ms660 (FOR VERY LONG) Working and working well are to completely different things! Same thing with the people making MS460 now selling it on YD100 crank webs. This main reason all your bearings on the crank blow. Over stroking the piston and dropping it below the walls to low as a result!
Stock cylinder design of a MS660 has a squish value of 1.6mm - 1.9mm. I know I know most fo you will have a mental breakdown after I say this! But if you try to get the stupid values of .6 or .7 like most want you will now have an open exhaust port directly into your crankcase area. At that point
you toss your top end into the garbage lol! If you would like to raise the compression. there is pistons with longer skirt so can drop the cylinder more! Or you can use a pop up piston and raise the compression that way! don't try get stupid value. I hear that so many times and this one main reason there builds run so badly!
one of the biggest issues most have. Is to much intake duration. I know this goes against everything most of you think you know! But dude to the size of the crankcase! which is way smaller than stock ms660 in volume. You will actually cause (bleed through) which is a situation that will over compress the area inside crankcase cause blown crank seals or air/fuel mix to be blown back through the carb. HUGE power killer!
32 degrees blowdown in this engine! You have to realize these are saw builds are jetted really large out of the gate (Factory) and use a Cat box for an Exhaust so 32 degrees is ideal for stock porting int hose terms! Most like it 25-28 degrees so not so harsh to jet or tune! 32 by no means is hard to tune!
I just wanted to get this out there! You all have to realize these are not ideal conditions for these builds. There is no bulletproof way without major custom mod work. This was the best case for what you all want to build without some major custom built parts to next level the builds!
YEs I know most will file and cut ports till they meet some stupidly over the top timing that adds that crazy 2% more power cause you know you need it since bike will only go 70mph with stock timing to start with.... LOL
ADVICE: Don't overthink it! This bone stock ported timing display Top half you see! did 65mph like it was not even trying on a 38T sprocket @ 3/4 throttle folks! Im 6' 2" and 265 pounds! If you need to go faster than that your in the wrong hobby to start with!
#video
#videoshow
#diy
#bike
#rider
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[@kirstenspencer3630]

Thank you, your explanation answers questions I didn't know to ask. Will undoubtedly save me time and money on my bike build..oh I subscribed...

[@BuildBreakFix]

Glad to help

[@LarissasilvaSilva-vl6fh]

So, if use the yd100 botton end you need machine 4mm of the cylinder base.

[@mediamate426]

link for the 120mm connecting rod?

[@BuildBreakFix]

you have to buy a whole crank with one. ebay one. like 35$ whle unit cut stock crank off it what most do easiest way/.

[@jamess7681]

I have a phantom 85 will this just bolt on

[@BuildBreakFix]

Ms460 jug has 50x54mm hole pattern. Chain saw file make ovals on jug to fit 50x50. And you will need 8m to 6m thread adaptors and 4 6mx15mm long allen head bolts. 12mm crisp pin.

[@jamess7681]

@Build-Break-Fix the stock jug blew up and I figured why not go bigger I was told the 54 mm jug will fit without having to bore out the case just drill some holes would that be better or should I stick with the 52mm 460

[@BuildBreakFix]

@@jamess7681 well honestly go 52mm version. Yes I have a 54mm but you need to upgrade bearings to like ceramic bearings or you wont last long! 52mm already pushing the max rating of operation for size and spec of steel types. Ceramic ones are not cheap

[@jamess7681]

The crank bearings?

[@coltonkirkman8714]

Can I use a K970 Connecting Rod instead of a K660, or K670?

[@BuildBreakFix]

To be honest no idea. Only used the one. I know a k970 for sure won't. Way to long. But a k670 I have never physically seen before in person

[@coltonkirkman8714]

@@BuildBreakFix so as far as you know I can only use the K660 right ?

[@coltonkirkman8714]

@@BuildBreakFix so what rods should I use with a yd100 crank on a 660 build?

[@KB_Joys]

I guess i got lucky with mine. I had bought a yd100 that was screwed up, the cylinder studs were drilled very poorly, causing the piston to rub hard on the walls, had no power, etc. So i bitched about it and got a refund. I noticed mine had a zmn100 rod and and bigger wrist pin. So i thought what the hell and plugged the holes and slapped on an ms460 jug. Well it didn't work out so well so i put an ms380 piston in and everything lines up great. No base gasket tho, but all the ports clear and reassure like 1.5mm squish. I need to go buy a chain and lock abd i can't wait to see whats up. Im hoping everything will be fine, as its my first saw build. Ive had it built for like 7 months and haven't fired it up yet . Kinda wondering about tne timing with the magnet, is there anything that i should know before trying to start it? Thanks.

[@JoshF89]

Thanks for your informative videos, I appreciate it. How did you make up for the difference in the crank pin? Is the wrist pin still 12mm?

[@BuildBreakFix]

the correct con rod uses a 12mm wrist pin anyhow! otherwise you need sthil conversion pin. to 10mm for like yd100 or bushing

[@anythingwithanengine8736]

Is the 120mm connecting rod measured from center to center or full length of the whole part?

[@BuildBreakFix]

Sorry I missed this! Center to center

[@anythingwithanengine8736]

@@BuildBreakFix great thanks!

[@Mark-n9y2t]

Where do uou get the high compression piston from Im bringing this one on a race track

[@BuildBreakFix]

Sadly pop-up piston on ms660 is OEM only item it seems. Reason is it's known to snap crank shafts. Ms660 is over 16hp lol factory on bicycle build. It's why you don't see many 87ftlbs torque roughly. Tears the whole rear end apart fast. It's why you don't see many actually run very long. Or at all on a bicycle. Mine twisted a felt faker frame like pretzel

[@KevinLunsford-je3rz]

I have been working on another build also! MS660 build! Problem is that i can not find the Husqvarna K760 piston rod by itself without buying the crankshaft too! What is the serial number for the Husqvarna K760 piston rod?

[@KevinLunsford-je3rz]

July 13,2024!

[@BuildBreakFix]

@@KevinLunsford-je3rz you have to go on eBay find one. Use a cut off saw on the crankshaft. It's what everyone does.

[@BuildBreakFix]

Sorry about the delay I was sick for a while then took a vacation

[@KevinLunsford-je3rz]

@@BuildBreakFix Thanks bro! Hope you enjoyed your vacation after being sick?!

[@Mark-n9y2t]

Building a hs 660 now just need info on what rod to use where to get pop up piston and specs for conversion or if you sell piston conversion kit

[@BuildBreakFix]

No conversation needed of you use the correct rod. Most look for an old Husqvarna concert saw 770 or bigger all same rods. They come on a crank factory. Cutoff saw is how most remove the crank. Fits perfectly on stock yd100 crank web and bearing. 14mm ms660 bearing fits wrist pin no mods

[@mikedraper453]

Bro, Ive been looking for that connecting 120mm. I cant seem to locate one. Could help me out with that like where you got yours?

[@BuildBreakFix]

They come in the cranks. Mose cut off saw the crank to get the rods. eBay 25$ to 35$ used one! They are hard to find everyone buys them up fast. OEM good lord. $$$$ for one to murder is crazy

[@mikedraper453]

Thanks bro, I think I found one. I'll see if it's the right one. Otherwise I'm losing out on 55.00 bucks and 8.00 shipping. Haha

[@wrenbrighton2358]

What type of Husqvarna saw did you get the 120mm connecting rod from? Read in the comments yoy need to buy the whole crank assembly then cut it to get the rod. Just wondering what saw the crank comes from.

[@BuildBreakFix]

760 or 790 rock saw. Ones you cut road to CV concrete with. Cranks are like 30$ on Ebay for decent used one. Cutting it in half anyhow lol

[@wrenbrighton2358]

@@BuildBreakFix Oh cool thanks so much for your help love the work you do man.

[@TStyleYT]

Anymore connecting rods I can get that’s 120mm that isn’t the brand you mentioned I need urgent help on that asap

[@BuildBreakFix]

what are you even asking? kinda lost me. you saying that cause of crank design for that rod? you need to buy the full crank and rod it how they are sold. most buy them off ebay just cut off saw the crank steal the rod only 35 to 40$ whole assembly. so not really sure if that is what you mean or something else?

[@smokinamby]

Can you clarify at 4:00 "crank pin bearing is not stock to fit this 24mm rod hole to 16mm pin" Are you referring to the wrist pin bearing that's in between the 2 crank weights? What do I need to convert it?

[@BuildBreakFix]

Carnk webs since they are round lol but are you asking the crank webs bearing dimensions? All in mm 24 od x 15wide x 16 id needle bearing. It's a 12mm wrist pin piston end 16od 14wide 12id

[@jamesgavel4239]

How much one of your motors you would sell?

[@BuildBreakFix]

Not doing anymore! Shipping has become a nightmare paired with out of stock items that never arrive you pay for to make them. Just was not worth it!

[@bradmarkus7768]

Do you have an email I can reach you at? I have some parts questions and would like to pick your brain a bit if you have the time. Thanks

[@BuildBreakFix]

[e-mail]