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Discussion Starter · #1 ·
I'm pretty new to these old bikes so before I dig I wanted to ask about it and hopefully somebody will have some suggestions.

The choke doesn't seem to do anything when starting the bike, when the bike warms up it idles like the choke is on when it's not and you can turn the choke on/off freely without any change to idle when the bike is warm.
I assume the choke is stuck on inside and the lever isn't working but like I mentioned before I'm pretty new.
The spark plug on the right is colored perfectly and the one on the right is black.

What's the 1st-2nd-3rd things you would check?

Thanks.
 

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stocker350 said:
I'm pretty new to these old bikes so before I dig I wanted to ask about it and hopefully somebody will have some suggestions.

The choke doesn't seem to do anything when starting the bike, when the bike warms up it idles like the choke is on when it's not and you can turn the choke on/off freely without any change to idle when the bike is warm.
I assume the choke is stuck on inside and the lever isn't working but like I mentioned before I'm pretty new.
The spark plug on the right is colored perfectly and the one on the right is black.

What's the 1st-2nd-3rd things you would check?

Thanks.
Check to see that the mechanical linkage between the two carb chokes is actually hooked up and functioning.
Pull the air filters off and you'll be able to actually see the choke plates in the mouths of the carbs.....
 

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Discussion Starter · #3 ·
Yes, the exterior linkage seems to be hooked up and functioning properly. Something I noticed last night while we were out riding is that the idle will change ocasionally when we are stopped.
 

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Have you checked to ensure the right side is actually firing. Are both header pipes header hot?

I'd check the following:

- valve clearances
- compression
- ensure spark is going to both cylinders
- timing
- carb float height
- drop in new set of spark plugs

that may help pinpoint the issue, at the very least it will rule out a few things.

Best of luck.
 

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What HerrDeacon says. Start any analysis with a complete tuning. Waste of time not to do that first. "Choke doesn't make any difference starting": Mine doesn't make much difference in warm weather. usually starts better with it open, will start with it closed but will run roughly, emit smoke if not opened very promptly. Given that the starter clutches are not possessed of eternal reliability, I almost always start by kick, easy enough as the motor starts readily. Expletive deleted starter button broken, anyway. ¶ The coked up plug: Soft fluffy stuff? Too much fuel or choked up air intake (not enough air), like squirrel's nest in the air cleaner. Run it without air cleaners. If you're not in a sand storm, it won't hurt anything. bit of wire screen over the intakes will keep large stones, etc. out of the cylinders. Make sure the float valves are closed and not leaking at the appropriate level or slightly lower. Definitely must not be to high; a little low makes no difference, I'll explain if you need to understand it. I think there have been comments about air leaks causing rich mixture - not the case in my experience. Make sure the pistons rise and fall unimpeded, that they drop all the way to the bottom. Piston up & throttle closed is a bit like a mechanical slide carb with the choke shut. ¶ Still cokes up? Carb problems. Tear down, immersion bath cleaner, soap & water, blow dry, put it all back together. Keep the carb top out of the cleaner bath - it isn't kind to plastic. Check jet values. ¶ Wet, oily stuff on the plugs - Ouch. Tear down. Rings, valves, guides, oil deflectors, gaskets... While you're in there, might as well do a full house cleaning - the details will only give you trouble later...
 

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Discussion Starter · #7 ·
Thanks for the tips. It sounds like I have a lot to do. Anybody have a link to a good step-by-step guide with pictures on timing and valves? I've never done it but I doubt it's beyond my comprehension.
 

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Oops! got it backward. "Piston up & throttle closed is a bit like a mechanical slide carb with the choke shut." - in fact, you'd have little or no venturi vacuum at low speed. You'd still pull fuel in for starting with the choke, which doesn't depend on venturi vacuum because the choke is before the venturi in the air stream. Depending on piston position and idle speed, you might not be able to get a reasonable idle without the choke partly closed. With SU carbs with idle problems that defy adjustment, whacking both sides of the vacuum bell with a screwdriver handle sometimes "fixed" the idle and told us where the problem was. Strombergs, which used a diaphragm, used to suffer from diaphragm leakage. They looked like a good idea, but gave more trouble than the SUs.
 

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Discussion Starter · #10 ·
Thanks for the help. I'm hoping to check the timing and valve adjust before this weekend. If that doesn't happen I can't get to it until early August.
 
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