CB200T only reaching speed of 30mph

[yonson88]

Hello All,
I have been working on a 1975 CB200T for a while now, cleaning and trying to get it running correctly. I finally have made it to the point where both sides are running evenly and starts easily. The issue that I am having is I cannot get the bike to get over the 30mph mark. It seams to run okay up to half throttle, but any more and the engine cuts out or sputters, sometimes backfiring. I have tried cleaning the carbs and feel the problem is in there still, tho want to know if there is some where else I should also be checking?
Any help or advice is greatly appreciated.
Thank you all!

 

[mark13018]

Is the intake and exhaust stock parts or have they been changed to aftermarket parts?.. 3/4 - full throttle uses the main jet and if it's bogging down in that range then the main jet needs adjusting to another size. The jets are readily available in different sizes. You may have to adjust your needle height too. You could always do that now too and adjust from there if need be. Keep checking your plugs also to look for abnormal colors to make sure it is burning the fuel properly.

 

[yonson88]

The intake is stock and the exhaust is aftermarket. The company told me that no re-jetting would be needed on changing over to there brand. But no way to tell as I bought the bike originally with no mufflers just headers..
Where is the best place to find new jets, also would I be wanting to go up or down in size or is that a test and check hassle??
Thank you!

 

[mark13018]

I buy my jets from a local shop for a couple bucks a piece.. We have about 5-7 shops locally and some sell parts like that and some don't. Maybe because they're in their service shop and they would rather you pay them to service it... Call around, those are keihin carbs and I think it has an 88 main jet? I may be wrong... Anyways that's fairly irrelevant, you need to know what size you have. Take it off and take it with you to the shop you find that will sell you jets.
As far as what you need for your bike there is no magic number. You need to "read" the plugs to know for sure weather you're lean or rich. Then you just need to rejet and check everything to make sure it's running properly. If not move up or down again. If you make the exhaust less restrictive it will have more air in the combustion chamber, therefor it needs more fuel so the jet needs to be larger.
You just have to keep taking them off, changing things and putting them back on until it's right. I would guess just to go one size up. I think it goes from 88 to 90 and if you need a 89 you'll need jet files.

Anyone else can add info or correct me if I'm wrong.

 

[deepwaterimports]

I'm having similar issues with mine and have been told a few different things, check the rear and front sprocket sizes they should be 15t up front and 35t at the rear.

clutch could be on its way out mine wants to go harder but keeps slipping.

could be electrical power from battery or stator rectifier not charging etc )if you keep killing battery's like i did)

id love to hear how it gets fixed mate as im in a similar boat.

i have new clutch rectifier and sprocket on its way and if its not fixed after that ill have to check stator and jetting and after that flame and fuel hahhahahaha

 

[acm177]

How high can you rev the engine while in neutral, without load? Does that work smoothly?

 

[teazer]

Have you given it a complete service, new plugs, points, condenser etc. Are valve clearances and ignition timing spot on? Does the Automatic Timing Advance unit move freely to allow the timing to fully advance? That's the weights and springs behind the points plate. If you grab the points cam in your fingers, you should be able to rotate it a little and it should spring back.

Clean and check your carbs and note what jets and needles are fitted. Knowledge is power - literally as well as metaphorically.

 

[deepwaterimports]

How high can you rev the engine while in neutral, without load? Does that work smoothly?

I have no issues there reeves out fine if its not I would recommend what teazer suggests carbies first then internals.

Teazer knows he's bikes extremely well and I would strongly recommend reding old cb200 or any bike posts he has posted in for help. I have and it's gelped me out a fair few times.

 

[carnivorous chicken]

You should verify that you have spark and compression on both cylinders.

 

[yonson88]

Thank you mark. I am going to try a few other things before changing the jets. Very good info to know tho.

Deepwaterimports: The sprockets are stock, and clutch is perfect, engine itself only has 120 original miles and new rings put in.

ACM177: The last time I tried got it to 8000 slowly creaping up to it and didnt want to go higher.

Teazer: I have given it quality time with setting the ignition timing, and valve clearances. New plugs, on third set now just in case they are fowling out. For the points I took a working set off of a running bike cleaned and re-gaped, also swapped out the condenser and coil and carbs from the running bike in attempts to figure out the problem. The Timing advance unit is working as should. Ive also gone threw the carbs twice..

carnivorous chicken: I have spark on both plugs evenly, also compression is 150 one side 145 the other.

 

[yonson88]

Ok, I am now able to get to 50 mph, havnt had it on a long enough strait-away to get any faster. The issue was the Automatic Timing advancer. Thank you Teazer, I had misunderstood you previously thinking you meant the spring action on the points itself.
I believe a nice carb adjustment will have it running even nicer.
Thank you all for your input.
Very helpful!