RD200 issues.

VonYinzer

VonYinzer

Over 10,000 Posts
Got the bike. Ran great. Looked great.

Went over her, tightened everything up. New plugs, new fuel lines, cleaned the points, etc...

Put about 1000 miles on the bike with NO issues whatsoever.

Than one day, my buddy Greg and i were about 40 miles into a nice afternoon ride and the left cylinder crapped out. I limped the bike home and parked it.

Finally get around to figuring out the issue a little later, and find a few things.

1. There were NO air filters in the housings. I have no clue how I over-looked that, but I did and its in the past. Luckily Rich had some pod filters that fit (sort of...) for the ensuing fixing/testing.
2. The left carb is dumping gas everywhere. Rich and I pulled it apart, and realize that the emulsion tube and jet have somehow unthreaded and were lying in the bowl. Jesus... Thats a new on to me.
3. The right carb, and after some work, the left carb are spotless.

So... Carbs rebuilt and set correctly (according to the manual of course...). New coil installed (why not?). New plugs. Points cleaned again. New fuel lines installed. Exhaust cleaned (kinda/sorta... Didnt want to take them apart completely). Pod filters installed. Cylinder head pulled, piston, rings, and cylinder wall checked (casually) and pass with flying colors. Thank christ for that, after the non air filter situation... Head torqued down to spec (head gasket seemed ok). Oil tank filled with fresh Yama-lube.

Turn her on, and one kick she fires. Then she promptly blows billowing white smoke out of the left pipe, backfires, and sputters between running and dying. (Left cylinder only) The right side runs great (though a bit hot...).

Give it ANY throttle and it dies. So, everything is pointing to a really rich left (and now, somewhat lean right) cylinder, but there is no reason for it. Not that I can think of anyhow. The jetting is the same in both carbs (forgot the paper with the numbers at the garage) and as stated, it ran GREAT up until it didnt.

So, any thoughts? Im afraid that theres a crack or some internal damage to the carbs, or at least the left. I havent been able to find one just yet.

Theres a chance that I may just go ahead with some top end work come spring anyhow, but dammit I want this bike running correctly when I put it away for winter here shortly. Im still a HUGE newbie when the two strokes are involved, so any help would be appreciated.

Thans in advace folks.

-Mike
 
mike..left cyl case is probably loaded w fuel seeing you had a jet unscrew..either suck it out w a vac and small hose or plan on changing a few plugs till you get the case clear...and it will prob take a few miles to clear the pipes/cases.. went to fire op my h2 the otherday to winterize it and after a few kicks found it wanting to hydro lock..so..carbs and petcock at least this winter...
 
You've probably washed all the old oil as well, going to be really smokey for a while 8)
All the oil pipes are connected up properly and pump set right?
I've had to remove shims several times on Yamaha two strokes as pump over delivers
It's easy to check,you use a feeler gauge and watch plunger moving in and out, stop engine when its all the way out and measure gap (instructions are in the manual)
 
Yup. Oil system is a-ok. Up until this issue, the only smoke was when the bike was really cold, but went away after a couple minutes. Im going to change the crankcase oil and grab a handful of new NGKs after work and go from there. I honestly havent done shit with it in a couple weeks, as I havent really had any time to dedicate to the bike. Hopefully I can get it going here soon and get in a few more days of riding before the weather really sucks. Thanks guys.
 
There is no 'crankcase oil'?
Case is sealed, the oil is for transmission/clutch only
It won't hurt to change it though.

Have you tried removing generator and 'lifting' crank?
The dynamo rotor is real heavy and tends to wear out left main bearing
(sorry to be 'doom and gloom', I pretty much only worked on them when they 'didn't run right' ;) )
 
Ya... Sorry PJ. I mean trans oil. Just saying that I was going to change all the things I could while Im there. Kind of a thinking out loud situation. Haha... And yeah, Ive checked for "play" as much as possible. Everything is nice and tight. The bike only has around 7500 miles on it and has been really well taken care of, thankfully. After work today Ill dig into it and recheck that stuff for good measure. Looks like next week will have some decent riding weather for a couple days, so Id like to at least get a couple miles in before its shitty here and the bike gets put away. Thanks again.
 
I'll have to drag my electrical manual out, haven't worked on the Yamaha dynamo for several years (about 1986 ;D )
You have checked brushes are OK?
They will be a bit worn at 7500 miles but should still be OK
 
Oh ya. Everything works great and looks great. Whoever owned this bike in the past had been VERY tame with it, and really taken care of it. The electric start works fine, both leads put out a huge healthy spark (enough so that it can be seen in the daylight...), and the bike is in time and the points are set correctly. Electrical issues were my first assumption, due to how it died, and have been gone over thoroughly.
 
I ran into an issue when I was done rebuilding by RD200... still working on getting all the kinks out. What It would idle fine but when I took it down the road with air box off it would bog down and die. I reinstalled the air box and it ran fine after that. My local shop advised that with the small 2 strokes they like to be balanced out with the air box, he suggested I don't put the Pod filters on.
 
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