Derestricting a Honda CB500

[@Lincento53]

I had my bike loose power out of nowhere, couldn't get past 80km/h, turns out the original sub air filter had fallen apart and got stuck in the carburetor, popped in another one that i cut to size from dishwasher filters. Also thank you for the video, I had difficulty finding how my bike was restricted, then I discovered and followed your tutorial and was very happy with the result.

[@memybikeni9931]

Ah great, glad it helped you out. I’m annoyed about the sub air filter material, mine was just dirty and I paid £11 from memory to get a Honda original replacement and then loads of people on the Cb500 forum said just use sponge. Glad you tried that 🤣 thanks for the comment, Rich.

[@tomasraumschussel3429]

Hi there! this comment is quite old but I need to ask... would the bike also die completely? I have mine doing that now and I also found a piece of foam inside. It suddenly dies on me. I hope this was the cause... otherwise I am at a complete loss! 🤣 Thank you all! :)

[@john-5959]

Thanks for the video, i had a bit of a different experience. Recently de-restricted an CB500 and i don't know why you disassembled so much parts to get to the rubbers, there was no need for removing the carbs and airbox. You should be able to get them out under 15minutes, you only need to loosen the clamps to the airbox(don't fully remove the bolts), unplug the hose on top of the airbox and pull the airbox back a bit to get it loose from the carbs, then loosen the clamps on the carb isolators(the rubber parts that hold the restrictor) and pull on the carbs towards the airbox to get then out of the rubber, now you have enough room to pull the rubbers off(might need a bit of help from a screwdriver to help them slide off) and pull them out to the left side of the bike and then remove the restrictor and mount it back again. So you only need to loosen 6 clamps and 1 hose to get the room you need to work with and the rubbers out.

[@memybikeni9931]

Thanks. I wasn’t sure how far back everything would come without fully removing it so just my way of doing it. Sometimes just easier to move things out of the way 😁 and I prefer not to take the inlet boots ( I’m sure that’s what you meant by carb isolators ) off the head if I’m being honest and risk breaking a good seal and creating a vacuum leak (they’re old) but good tips for others to have a go at. This was just my way of doing it.

[@1337PB]

Hi, do you know if there is a manual somewhere to do this?

[@memybikeni9931]

Well with any bike, just use the standard Haynes as this is just a basic carb removal. The restrictors will sit between the carb and the block in the inlet manifolds.

[@Pmmpe99]

Nice vid man! Only one thing has been left out. The CBs that are factory restricted to 34ps(25kw) has longer springs in the vacuum chamber, so even with the free flowing intakes it wont run at full power because the needle wont reach its peak point while u open the throttle fully!(check or measure it, resticted ones has 110mm long springs while unrestricted ones has 100mm long ones, and 125 main jets instead of 122) If you are interested in it, join the CB Owners UK they gathered plenty of infos in their facebook group.

[@memybikeni9931]

Thanks, I didn’t know that. Its possible this is a local regulation in your country ? Not sure if it’s the same in the U.K. I’ll check them next time if have them out of the bike. thanks for the comment.

[@soggybottom3463]

Thanks, great movie and explanations. Definitely time to change those plugs seeing the crud build up on one of them there, great job.

[@memybikeni9931]

Yes they had the right colour to them but no sense in not changing a cheap plug, especially when you have the hassle of getting the tank off to change them.

[@hni7458]

@@memybikeni9931 No, you don't have to do that. You can easily reach them from above, from under the tank, no hassle at all from L side. Use tools with right length, that reaches ~10 mil above the cyl surface. A little tight from R but no worries there either. Dear me, out on the motorway, you must be able to reach a spark plug w/o removing the tank.

[@memybikeni9931]

@@hni7458 Well to be honest it doesn’t look doable to me, but if you can and have then fair play. As for being on the side of the motorway, who’s changing plugs while out riding, let along carrying spares with them ? In this case I had the tank off anyway for better access to the restrictors and carbs

[@hni7458]

@@memybikeni9931 Sorry mate, you have helped me a lot with your efforts and your camera. But please try my tip, 'cause I'm really a layman and it's a no-deal to me.

[@memybikeni9931]

@@hni7458 I’ll certainly attempt it at the next possible opportunity. Glad you get some benefit from the vids, I’m just a lay person too so it’s always good to hear others successes like yourself, where I have failed. We live and learn All the best. Rich.

[@rctractif]

Pc 26 or pc32 engine?

[@memybikeni9931]

No idea sorry.

[@disruptivegarage]

a nice alternative way to find out if they are there, magnets

[@memybikeni9931]

Assuming they’re not stainless yeah.

[@disruptivegarage]

@@memybikeni9931 good point, i cant imagine them going stainless, considering cost and all that

[@memybikeni9931]

@@disruptivegarage I think you’re right but the ones I took out had zero rust on them, I would have thought they would get some moisture damage if they were mild. I have them knocking around in my toolbox somewhere I’ll have a look and see if a magnet grabs them.

[@firstfist2351]

Very good explanation👍🏻

[@memybikeni9931]

Thank you 🙂

[@wesley8096]

Thanks for the video, good preparation for simple maintenance, and attended me to also buy the sub-air cleaner

[@memybikeni9931]

Glad it was useful, nice easy job overall.

[@wesley8096]

Mine was restricted to having only 25kw. It was more than just a washer, it was limiting over 50% of airflow. I have a question for you, do you know if I need to adjust the carburetors for the right air\fuel ratio? The bike is running much smoother, except for idling if need to rev it a couple of times to keep it going

[@memybikeni9931]

Hi Wesley, as a rule the carbs should not need adjusting due to the restrictor removal no, as for the jetting or mixture that’s the same before and after. The restrictors when you think about it just stop the bike from being able to breathe as fast when the intake stroke pulls air/fuel in so the slower or restricted air flow just pulls less of the same mixture through. However, Idle speed may be just needing turning up a notch though, that’s the yellow screw on the front, I recall I did the same. lastly, would be worth just having the carbs cleaned and balanced, as having said all that the pilot jet one or the other side may be crudded up and that may not have been an issue when it wasn’t under such load. Carbs are now working harder of course. These keihin carbs are usually very good so recon it’s a tweek anyway. Rich

[@wesley8096]

Spanner Monkey Great explanation, makes perfect sense indeed! I was planning to turn up the stationairy screw anyway, but now I can drive without fearing a poor air/fuel mixture, thanks alot again

[@attilaendresz5106]

Nice work, congratulations! I would like to rebuild the restrictor. Can you help me? What is the hole diameter on the restrictor plate?

[@memybikeni9931]

I don’t know precisely, but if you are restricting a bike for licensing reasons it needs doing by a mechanic that can certify the bike afterwards, depending on your local regulations I would imagine. It is just a simple washer same diameter as the inlet, I’d say the hole was about 12mm.

[@attilaendresz5106]

@@memybikeni9931 Köszönöm szépen! :)

[@memybikeni9931]

@@attilaendresz5106 you’re welcome.

[@stanislavbriza812]

Did you have to re-jet the carbs or was there any other restriction? I did same with cbx650 and the engine definitely runs better, but not as quite as it should be. I wonder if there is any other restriction like smaller main jet or something limiting the throttle in the carburettor. Is your bike now running full power?

[@memybikeni9931]

the restrictive washer is all thats fitted, with the original jets so no rejetting required on removal. she runs full power yes, but is a bit down on compression which is another matter 😊

[@teglashunor9321]

Hello, can you tell me where is the fuse box?

[@memybikeni9931]

Hi mate, yes it is under the right hand side black plastic side panel.

[@Zjones55555]

Hello I need help. I have removed the restrictors from the carbs, put everything back together and my bike will not start anymore. I got it to run but it would die if i took the choke off, and now it just will not start up again. Has removing the restrictors unbalanced the carbs or do I need to put them back in to run :( I am at a loss

[@memybikeni9931]

sounds like you need to get the carbs back off and clean the air and fuel jets and ensure the mixture is set correctly. You shouldn’t really need to but where there is more load on the system now, it may not be able to cope with the right air fuel mix as it did before if they are blocked. If you left the choke on for longer and the main jest took over I imagine it would run. could be just a carb service. also, check the float bowl fuel level is ok. it’s trying to work harder.

[@ivan868]

What is the "restrictors"?

[@memybikeni9931]

21:32 shows you the restrictors in situ with the tank off and carbs out of the way. They sit in the recess of the inlet rubbers between the carbs and the head, just a couple of restrictive washers designed to reduce the bikes power output to meet licence requirements, not needed so I removed them. I bought the bike like it, but I have a full DSA any size engine/power licence. Hope it helps.

[@janisciemgals7644]

need to replace wiring loom, but airbox mess with wiring loom with itc connectors get from bike right side ( where fuse box is) to left side ( voltage regulator). there is a possibility do this without removing air box, what do you think?

[@memybikeni9931]

Hello mate. The wiring loom is quite easy to trace around the bike, and a lot easier to do with everything out of the way. The tank, carbs and air box come off in about 15 minutes and would make it a lot easier to work on. That's the way I'd go. Good luck with the loom mate,. What is the issue anyway ? Couple of years ago I thought I may need to do the loom as the brake and tail light weren't working but I traced the fault to the brake wires before they connected into the loom fortunately.

[@janisciemgals7644]

yes, prove, that all was good, and wiring can be changed without airbox removing. in my case all start with short-circuit between mass and +12v in voltage regulator. that blowns out constantly main fuse ( 30A). then in another day i want to test voltage regulator again, and connect it without connecting mass point, who is about on voltage regulator - that was my fault, and in result, i have smoke, and completely melted isolation from wire, who go to sidestand. another direction of that wire is in main wiring loom. firstly i think, all not very bad, and i can ride with that till autumn, but in last ride i get short circuit in 15A fuse circuit. i decided, then, to change loom completely, because wires is melted in loom, and there is almost impossible to do all good as previous. sadly, but in new loom ( from cb500 2000) front connectors differ from my old. i have cb500s 1998... try to sort out that mess and connect as it must be in next weeks...

[@memybikeni9931]

It's odd there are changes in the loom from 1998 to 2000 as there were few changes to the bike during its life. The loom I imagine is off of the cb500s as that would have had different lights at the fron so probably different connectors unless they were just upgraded. Hopefully the new loom will sort the fusing issues anyway.

[@janisciemgals7644]

i hope so :D now try to get anyone, who can give me cb500 front loom connectors pics, for i can understand, what connector where goes to...;)

[@memybikeni9931]

Well main thing mate is get all the right connections on the right loom, lay the loom out and follow the loom round the bike until you're sure where everything plugs into and where everything wraps round, it's not too complicated, then take loads of digital pics. That bit is fail safe. I stripped the CB500 engine down and it made it a whole lot easier to have pics to follow going back.

[@BUZZK1LL2000]

Anyone got any tips? My carbs are ready to pull out with everything disconnected and clips off but they won't budge even with a prybar :/

[@memybikeni9931]

You have the tank off right ? Something somewhere has to be attached, which way are you trying to extract them ? Up and out with the tank off is the easiest way and you can see all of the breathers and cables etc.

[@azibizaable]

Hi, I have dismantled my cb500, same as yours and I have problems mounting back things, can you or someone help me how the sidestand electric wire is routed up to the sidepanel main harness ?

[@memybikeni9931]

so it runs to the front of the bike underneath the engine mounting on the left, then over the top of the gear changer to the inside of the frame of course, and then in font of the sprocket cover but behind the same bracket that holds the water hose coming out of the water pump that heats the carbs. from there it runs up in front of the sprocket cover and the disappears in just behind the starter motor, from there it just runs back under the air box and out again to find its way to the green female box connector under the side cover. Hope that helps not easy without pictures, but I’ve just taken the covers off and it seems straight forward.

[@azibizaable]

@@memybikeni9931 I undertand now, you are very clear, I am restoring it pretty close to its original form, not making a project out of her or modify. Thank you from the bottom of my heart. Who would it think a guy from a rural village from Romania gets help from a guy from UK (if I'm right) just like that, its 2020 I believe. I have a Heynes manual but pictures are crap. Thank you !!

[@memybikeni9931]

@@azibizaable You’re right Haynes isn’t the best and very often wrong. I’m from the UK yes and it’s great to be able to reach out to others around the world in an instant. And when I saw your question my eyes lit up as it was a chance to get the tools out and have a poke around. I’m glad you’re restoring to original, mine is also original and I’m keeping her that way. I’m also about to restore a 1983 CX650 Turbo also to original if possible. Good luck with yours.

[@neilwiddison6529]

Great vid. Sub air filter wondered what that was will check mine. Thanks.

[@memybikeni9931]

Hmmmmmm... I replaced the filter with the correct Honda material, about 11quid. Others on the cb500 forum just use a bit of sponge so I wouldn’t splurge too much. LOL. 😂

[@benchristie6426]

where is the fuel line coming from.

[@memybikeni9931]

Hi Ben, not sure what you mean exactly, if you could point to the time marker on the vid I can give some assistance, there are a variety of lines to disconnect from tank to carb and breathers etc, even water heating for the carbs.

[@benchristie6426]

Can you take the picture under the cabs and the line conncted to the tank please and withour the airbox

[@benchristie6426]

Because I had replace a new cabs on the Honda CB500 year 1999. Because it was blocked and wouldn't come undone.

[@memybikeni9931]

Did you take the tank off ???

[@memybikeni9931]

Are you just trying to see where the fuel line runs into the carb from the petcock ?

[@Ladosligese]

been looking into getting cb500 with 15 k miles on it .. kinda cheap .. only its restricted to 48 bhp as danish state law requires for small license , but i can ofc hit the "big" license and go ahead on the 57 bhp .. so is this the process i gotta run trough ? .. beside the plugs ect ofc to get it back up to 57 bhp ?

[@memybikeni9931]

Yes this should be the only restriction.

[@mociczyczki]

@@memybikeni9931for 34 bhp verison like in mine is also main nozzle in carburetor 125 this must be also change for 122 for now i only put out those lamina restrictors in Edge of the carburetor like you in yuour video and bbike start to jerk and wobbling sometimes like it have to much fuel air :x so in me case main nozzle 122 must be also put on im waiting for this nozzle beacuse now i cant drive this bike you never know when it start to accelerate at all what it got and when it start to accelerate like 20 bhp :x

[@memybikeni9931]

@@mociczyczki it’s different rules on what the restrictor consists of I imagine in your country. I’d say if the bike is running poor.y now the washers have been removed it’s not getting enough fuel/air at all, so the re jetting should sort that out. Give the carbs a good clean while you’re at it.

[@mociczyczki]

@@memybikeni9931thanks for advice but why main nozzle is biger in restricted version to 34 bhp =125 than for derestricted veriosn =122 or is just some numbers which dont mean to much ? if you say it need more fual air ?

[@memybikeni9931]

@@mociczyczki not sure if your country’s regulations state the jet has to be that size with the restrictor, it may be the wrong jet was fitted in the first place or someone fitted it after restriction thinking that would counter the power loss, which it won’t. jetting shouldn’t make a difference really, the restrictor is just taking less of the same mix. A bigger main jet will assist with cooling on an air cooled engine, you get that with v twin air cooled units. it possible the issue you have at the moment is the engine is trying to work the carb harder now it has better flow and the carb may just need a good clean and service.

[@felixchale9691]

Give me bearings men and con

[@memybikeni9931]

erm... ? nope I’m lost !

[@Алекс-й2р2з]

Привіт із України

[@memybikeni9931]

Thank you and wishing you and your countrymen all the best.