New stock CL350, just rejetted by mechanic. No power under 3k RPM. Stumped...

so2002

so2002

Been Around the Block
Hey Guys,

My first post here. My first bike. A 1970 Honda CL 350. Completely Stock. Just bought it, but was noticing this issue. Worked a deal with the owner to take it to a mechanic for a tuneup. 15 days and 3 jet sizes later (today), I picked it up from the mechanic. On my ride home, I noticed that it has the same issue. The mechanic was an extremely rude and unfriendly guy (but supposedly reputable according to the seller, and with a garage full of cool stuff), and he is on vacation for the weekend.

The problem:
Every now and then, at a stop, I can't get the bike up to speed. It gets stuck in the 2k-3k rpm range. It's as though it goes completely limp. Even if I put the clutch in, the RPMs stay at the same range or decrease (sometimes totally dying). If I try to start the bike, it starts right up without any issue and I can ride right off like it never happened...until the next light. This isn't at every stop, but I noticed it got more frequent the longer I rode it.

Some observations:
  • I noticed that there is sometimes a hesitation in the throttle, even though I can see it moving the carb.
  • Sometimes when I press the clutch in, or rev in neutral, the RPMs fall very slowly.

For now, I realized that I can just rev to 3k rpm and feather the clutch. But I would like to figure out what's happening here. My first thought was the carbs, but I want to believe that the mechanic tuned it properly. I'd love some suggestions!!!

cNLv29x.jpg
 
Looks good out in the sun
Where are you?
Stock airbox?
You will have issues with 'pods'
Very few people know how to tune stock Kei-Hin '3 jet' CV carbs, you can't use the same methods as Mikuni (even Mikuni CV)
Unless he was a Honda mechanic in the 70's he probably doesn't know enough about them (a reason to be rather gruff - doesn't want to admit he can't fix it)
 
I want to believe the guy did something properly, but I'm still thinking that they're the issue.
  • Stock airbox, stock air filters.
  • The battery is fine. I can start it with the electric starter if it was running immediately prior.
He said he thought it was running lean with the stock jets in. Since everything is stock to my knowledge (prior owner was particular about it), I don't see why larger jets would be in there.
 
May have an air leak somewhere or float levels could be too high?
Could also have oxidation inside jets or emulsion tubes (that's always a 'fun' one)
Carb cleaner sprays through the holes so it's assumed everything is OK
 
so2002 said:
The battery is fine. I can start it with the electric starter if it was running immediately prior.
Click to expand...

But you can't start it unless it was running immediately prior?
 
Day 2 Notes:

  • Battery is fine, the starter worked effortlessly on first crank, and all the rest. The battery has plenty of cranking power and churns for a long time (though it makes crazy sounds!)
  • The problem is intermittent. While it definitely doesn't have much power in the low RPM, there are times where I can't get it to rev above a certain RPM.
  • When I feel this loss of power, letting off (feathering) the gas can sometimes allow the RPMs to build. Otherwise it generally dies, but starts up 15 seconds later without issue. If I manage to keep it reving and not die, I can get the RPMs back after 30 seconds or so. (and then it works fine)
  • Sometimes I have great acceleration, sometimes its so-so. Regardless, I haven't been able to get the RPMs over 8k or so (before and after the mechanic's tune up)
  • Seemed to run a little better with a full tank of gas
The jets are new, and there is a new fuel line.


I just don't get what could be happening here. The bike will run fine, with multiple stops. But then I'll come to 1 stop, not be able to build RPM (even in neutral), and the bike dies. But then it will fire right up and work like a champ.
 
Yep, starting to sound like a blocked tank breather, although the 8k limit could be old points with weak springs?
 
Letting the tank breathe didn't have an effect. The bike still falters at low RPM and taking the lid off when it couldn't rev over 2k rpm didn't have a noticable effect (60 seconds later, it was working again)

New Notes:

  • The bike seems to behave better and have more power when the engine is cold. It was only after around 10 minutes of riding that it started having these issues.
  • Taking the gas cap off didn't have any effect

The previous owner set the points, but did not replace them. I assume they're original.
 
Running better cold is generally too rich could also be faulty coil overheating?
Do you have a timing light? (cheap one from Harbor Freight tools about $20.00)
You can connect it up (inductive) rubber band the trigger and see if spark stops or gets erratic (and check your 8k problem)
 
The weather has gotten colder the past two days (~65 instead of 80). The bike seems to be running better in general, might be the fact that it's colder, might be the fact that I've now put two tanks of gas in it. That being said, all is still not well.


Yesterday, I went about a half hour before I started having the RPM stuck/engine dying issues. On the way home though, it was much worse, and happened several times.


This morning, I took the bike on the freeway. Here in chicago, there is a lot of morning traffic. The bike handled low speeds (down to idle) in first gear and had no issue with the RPMs as long as I was moving. (It seems like this problem only occurs when starting from a standstill). I hit an open section and went through the gears. She pulled hard and what a great sound!!! (Still, not more than 8k though). When I slowed down for traffic and put the clutch in, the engine died nearly instantly. Took a couple starts to get it going again, but then it was fine.


Still trying to figure out this low RPM problem. I shouldn't have to slip the clutch from 3500rpm to get going (but that's the only consistent way to avoid this)

I'll look into a timing light, I should probably have one in general.
 
Carb sync is right? It sounds like it may be only running on one cyl at idle~3500rpm
 
Hmm, so new issue now :mad:

The bike won't idle above 1k-1.5k RPM. Can't even ride it now.

PO says that the petcock has a screen in it instead of using fuel filters. I don't think a clogged filter is the issues, because there is plenty of fuel in the fuel lines, in fact, more than usual. (Problem still occurs when I turn the petcock to the off position)

Help? :'(
 
Take the carbs off and clean them. While they're being cleaned, check compression and timing.
 
Probably lost or tossed the rubber plugs over pilot jets?
Unfortunately your going to have to DIY, as local mechanics probably don't know enough about early Honda's
 
Have you checked the auto advance-retard mechanism? If that is sticky it would explain those symptoms.
 
I just ordered the Carb Rebuild kits for both sides from DCC. Going to tear it all down this weekend. Thanks for the input so far. How would I check the Auto Advance-Retard Mechanism?
 
You must log in or register to reply here.

DTT Light or Dark

  • DTT Light
    • www.jadusmotorcycleparts.com
    www.lostapostle.ca/
    www.sparckmoto.com

    Spread the Love

    Back
    Top Bottom