Top End bog....crank seals ? 86 250r

[250arrr]

Hey guys new member here..I was finally able to get myself an 86 250r my 1st one. It starts on 1st or 2nd kick
and idles good. Compression is good...bike is completley stock. Stock carb with stock 86 jetting..42 pilot and 145 main.
I'm at sea level.. carb was sonic cleaned but the slide has the chrome plating worn off on one corner. 93 octane with
32:1 mixture. B8es plug gapped at .18. Bike feels good from low to mid but falls flat on top, almost feels like a miss
fire at full throttle almost like its bouncing off a rev limiter. You guys have any ideas ?

Bad

crank seal ?
clogged silencer ?
bad reeds ?
worn carb ?

[Shawn Powell]

Could be all of those things. I'd start with easy / cheap stuff. Check the reeds. The plating on the carb alarms me but I don't think it would do that. Can you rebuild the factory silencer on those? If you can be with the 10$ in packing and your time. I'd also check for air leaks, base gasket especially. My 500 used to blow em. Opposite effect though. Ran like a demon until it didn't run at all. Also possible CDI , but doesn't sound like it. Check all your electrical connections and wires. A bad ground could cause it. Although I've never seen that actually happen but people say it all the time. Good luck. Post some pics for the nosy people. And welcome to the site.


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[shortline10]

On a two stroke I always start with a compression check but the common issue with your symptoms is usually the CDI .

[yaegerb]

Hey guys new member here..I was finally able to get myself an 86 250r my 1st one. It starts on 1st or 2nd kick
and idles good. Compression is good...bike is completley stock. Stock carb with stock 86 jetting..42 pilot and 145 main.
I'm at sea level.. carb was sonic cleaned but the slide has the chrome plating worn off on one corner. 93 octane with
32:1 mixture. B8es plug gapped at .18. Bike feels good from low to mid but falls flat on top, almost feels like a miss
fire at full throttle almost like its bouncing off a rev limiter. You guys have any ideas ?

Bad

crank seal ?
clogged silencer ?
bad reeds ?
worn carb ?

Only way to rule out seals is to do a crank case pressure test. And as shortline suggested, a static compression test wouldn’t hurt.

[atc300r]

Try a new coil. My 85 250r had same symtoms a few years ago. I rebuilt the carb,changed the crank seals and bearings,new reeds , different exhaust ,and so on. It turned out to be coil.You should also check the other things mentioned above.

[250arrr]

Will do guys...thanks for the advice. I just ordered a new coil along with a 38mm pwk airstriker carb. I don't have a leak down tester...hopefully the coil fixes it. Only cdi I could find was a generic off of eBay for $13..you guys think I should try it or a waste of time ?

[fabiodriven]

Has it done this from the time you bought it? It could just need jetting.

[axeman24]

another vote for cdi i went through these exact symptoms recently i went through everything and played with the jetting till the cows came home then listened to everyones advice here and got an OEM OEM OEM CDI not aftermarket definitely not Chinese
i know for my 85r they are discontinued by honda and is a one year/model cdi i have an extra one but i believe the 85/86 are different but someone can confirm that
im sure someone on here can help you

[250arrr]

I bought it not running..i sonic cleaned the carb and put in fresh 93 fuel with 32:1 bel ray oil. Replaced exhaust seal amd gasket and added a fresh plug. Starts 2nd kick. I was thinking the carb could be worn so I ordered an airstriker.

[250arrr]

Anyone know where I can find an 86 oem cdi ? I only saw china ones on ebay.

[axeman24]

post up wanted ads everywhere you can i found mine on a vintage honda page on facebook

[250arrr]

Well a new coil didn't fix it..but i was able to locate a used oem cdi so I'll try that next but it wont be here for a few days. I also sprayed brake cleaner around the base area and around the reed and carb boot area with no changes so Im guessing no air leaks. Tomorrow im gonna try cleaning the ground and put on a pwk 38mm air striker. Was thinking of doing new reeds to or maybe doing the rad valve...what do you guys think ?

[Shawn Powell]

Idk how much reeds are but if you haven't done em in a long time couldn't hurt. If there older and getting worn they might not be opening fully wich could cause your bog. Not familiar with the rad valve. Just speaking in general.


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