Honda-SOHC
SOHC.co.uk Forums => SOHC Singles & Twins => Topic started by: alfiembra on November 25, 2019, 02:16:44 PM
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I have an 83 cb125tdc superdream that despite my best efforts I cannot get it to run properly.
It has decent compression 120psi LH cylinder 130psi RH cylinder, and has good spark on both plugs, valves all adjusted correctly and timing marks all line up.
When I try to start it from cold and on the choke, it turns over for ages before it fires, when it does it just about explodes revs straight up to 6/7k revs then dies as soon as I try to back off the choke. Sometimes it will run thereafter after a lot of turning over again but there is a noticable weakness on the right hand exhaust compared to the left and right runs hotter than the left.
I'm lost for ideas what to check next Looking for some guidance on what I could check next to get it going again.
Thanks
Alan
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Is it twin carb?
Sounds like blocked jets. Airways and or leaky O rings
Try carb rebuild kit.
You can also get aerosol carb cleaners. Ideal for squirting down narrow passageways
Sent from my SM-A750FN using Tapatalk
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Hi John thanks for your reply, Yes it's twin carbs.
Forgot to mention that I've stripped and cleaned the carbs twice, in an utrasonic cleaner, also got a second set of carbs and swapped jets around to no effect. Looking at the jets all look clear and no obstructions.
I had similar thoughts to the leaky airways and have tried spraying WD40 all over the carb rubbers with no difference to the running
I've also tried a 2 into 1 inlet manifold from a CM200 and can't get it to fire at all with that.
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Your compression readings look a bit low to me are they done with the throttle and choke wide open.
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Does seem a bit low, i worked on a C50L that had 115 but exhaust valve was burnt, got 150 with new valve
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My 350 has very nearly the same compression ratio and if I remember rightly that was around the 160psi mark.
Just had a look at my old cb350f thread and they were all,between 155 and165psi
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Your compression readings look a bit low to me are they done with the throttle and choke wide open.
Yes full throttle no choke, didn't think they were too bad at 120/130 but not sure what I could do to improve it maybe some oil in the bores and redo the test to see if that brings them up at all?