Carb/choke question

[RDDave]

I am STILL struggling with the left cylinder on my stock RD350b. It runs a good 30* cooler than the right and fouls plugs. I have swapped most of the ignition components left to right. Both cylinders have about 95# compression. I have had the carbs apart repeatedly and reset the floats, swapped floats, etc. Changed the left exhaust pipe. Iridium plugs really helped and I can clean them and bring them back to life.

My question is about the choke. I capped off the transfer tube and the right cylinder plug is clearly lighter making me thing it was getting too much fuel, too. The needles are all the way down and the mixture screws are out about 2 1/2 turns. The bike starts first kick and runs real good until it fouls the plug.

I have the left carb apart (again) including the choke assembly. I do not see anything wrong with the rubber at the end of the plunger. No nicks or cuts or deformation. But I would like to block it just to see if it makes a difference. The thing is; I don't know of a good, reversible way to block it. And, if needed, how do you service that plunger? Is the rubber removable and serviceable? Doesn't look like it.

Any thoughts on this would be GREATLY appreciated.

[RDnuTZ]

didn't you say you had another different Left side carb you could swap on? I'd do that before anything else- if it still has same problem then it's probably not a problem originating with the carbs themselves.

[m in sc]

does the lever have free-play when the choke is 'off'? if not it may be hanging open a hair. if the lever was put in int he wrong order or the 2 lifting tabs are bent, it can do this. you should be able to 'rattle' the ever around a tiny bit w out moving the plunger. if not, that may be an issue. .02

[KANDY]

Just a thought, at 95 psi compression, could there be losing ignition on one cylinder because of blowby.

[RDDave]

I need to post a pic of the extra carb. The emulsion tube in the main well protrudes out to where the main jet from the original carb won't fit. I don't know if that is correct for that carb or not.

I will check for the free play in the choke lever. Judging by the lock tab, it was original and had not been apart. Until now.

And I had thought about the low compression. Both cylinders are the same, within a couple of pounds. I wonder if one can act this way but not the other?

I will check these suggestions out hopefully tomorrow and maybe get a couple of pics and figure out how to post them of the original carb and the extra that I have. I would like to swap them to test. The emulsion tube protruding out is the only hold up that I can see. Other than that, the carbs appear identical. But the extra carb was in with a bunch of spare parts so I don't know it's lineage.

Thanks for the suggestions. As I said before, the bike starts and runs very good. I just need to find and fix this plug fouling.

[RDDave]

OKAY, with the help of this board; I THINK I GOT IT!

But first, you have to promise not to laugh. What I thought was an emulsion tube protruding from the main well on my extra carb turned out to be a pilot jet somebody had screwed in and tightened.

Now, I completely disassembled both my original carb and the extra carb. Went over every piece with a magnifying glass, blew brake clean through all the orifices, compared everything side by side and swapped everything possible from the extra carb to the original. Plus, I spent extra time with the choke assembly. I didn't do anything with the right carb or anything else on that cylinder.

Put the carb back on the bike, and at start up, the idle was way high.....too lean. Okay, that's a difference right off the bat. Took it for a 15 minute ride spending time at all throttle positions. It is crisper and the idle is still too high. Got back to the shop with both cylinders running. Another good sign. So, I checked the temps and lo and behold the left was hotter than the right. 208 to 190. Pulled the left plug and it was white. Obviously too lean. But given that I had pulled as much fuel as I could with the adjustments, that is to be expected, NOW THAT THE PROBLEM HAS BEEN FIXED. YAHOO!

I hate it when I change several things at a time and in doing so, fix the problem but do not know for sure what actually was the problem. But I was frustrated and just wanted to move forward. So, here is my suspicion on what was and is going on:

Either the pilot was too large or the choke was holding open on that left cylinder. That was why that cylinder was colder and fouled that plug. With the left cylinder down on power, the right was working harder, bringing it's temp up. Does that make sense to anyone else?

Now, the right cylinder is colder than the left because it is not working as hard anymore dragging the left. The left now is too lean due to me pulling as much fuel out as I could so it's temp has gone up.

I will readjust everything now and that should bring it all in. I do want to add fuel BEFORE I ride it any more because it is too lean.

Thanks guys. I wonder how long it would have taken me to get this lined out without your input? Maybe never. You gave me plenty to think about.