Problems with right hand carb idle screw

Q

Quilty

XS650 Enthusiast
Messages
60
Reaction score
0
Points
6
Location
Dublin, Ireland
Hello guys I'm new to this forum. I joined because I've seen a lot of good advice so far but I am beginning to have problems with a restoration I'm currently undertaking. So I'll begin. I have just bought a 72 xs2 and I'm pleasantly surprised how easy it is to work on compared to a harley. Anyway I've taken the carbs off to see what the way previous owner has set it up. There's a 125.5 main jet 42.5 pilot and a 125 butterfly plate correct needles and gasket, slides diaphragms and needles are all in good shape. They just needed a bit of a clean up so I got some petrol out of the tank and proceeded to clean. Carbs back on the bike, tried to tune using dead cylinder method left plug fine but ran hot and sooty right plug cuts out and runs cold out of the exhaust. Also no idle screw response at all on the right. I'm guessing the left cylinder is running at 1000 ( hence the soot on plug) and the right isn't however they both seem to be firing. Also I should mention that a tug of the individual butterfly on the right gives a stuttery and boggy response
I'm gonna swap the mains for 130s as stock but I'm at a loss each carb is set/ tuned to factory spec execpt for the main jet and needle at no3 pos not no4 can anyone help
 
No response on the mix screw can be an indication that the float level is off.
 
Floats are good both set to 25 mm one carb was leaking badly and that's one of the main reasons I took the carbs off. I should have new float needle and valves in the post tomorrow from Heiden tuning.
 
Ok changed the float needle and seats on both carbs set floats again to 25 mm tore the carb down again and cleaned, no blockages or anything else. Left carb had some oily residue in it maybe unburnt fuel mix? Not sure. I'm thinking it's maybe a timing issue
 
When you set the floats, did you measure them twice, once from each side, checking each float "bulb" individually? Many times the floats are twisted or tweaked on the mounting bracket and sit at different heights. You won't catch this unless you check both sides. If they are twisted, the fuel level could be anywhere, and most likely not where you think you've set it at. Twisted floats are very common too.
 
Yep I measured both sides here is a video I took let me know what you think
There's a little white smoke out of that exhaust aswell
 
Found the problem it was a cracked float. 2 miniature cracks. Need to find a soldering iron or is there another way to repair without solder??
 
Solder is what you need, and the repair isn't easy; overheating the float will cause it to collapse as the air in it it cools. If you want to try it, use a low temperature solid core solder with plumber's flux, not rosin. New floats are still available, and replacement is usually a better idea.
 
Right, I bought a new float, new plugs still no change. I'm starting to think I bought a Lemmon here. I should mention that there is a small hole in the exhaust pipe where the pipes meet the muffler there is white smoke coming from the exhaust. Is there a connection. carbs are double clean. Floats set correctly. I really don't want to take the carbs off again I would appreciate any feed back at all before I call the AA to bring to a mechanic
Thanks a million
 
Quilty said:
Right, I bought a new float, new plugs still no change. I'm starting to think I bought a Lemmon here. I should mention that there is a small hole in the exhaust pipe where the pipes meet the muffler there is white smoke coming from the exhaust. Is there a connection. carbs are double clean. Floats set correctly. I really don't want to take the carbs off again I would appreciate any feed back at all before I call the AA to bring to a mechanic
Thanks a million
Click to expand...

There's no such thing as a lemon; only problems that can be solved.

Calling AAA to bring you a mechanic is just about the worst thing you can do. I can almost guarantee you that they will charge you a lot of money to do close to nothing. If you can't figure this out, you should sell the bike, this is part of owning an old bike.

That being said, we've all been here. I'm guessing this is your first old bike you're really diving into. This is what separates the men from the boys.

Your bike only needs a few things to get a bike to run: fuel, compression, and spark. Are you 100% sure that you have all three on both sides? After that, set your valves. After that, timing. Have you done these two things? Are you sure? If not, you shouldn't even be thinking about your carbs.

Now, AFTER you have set all those things, it's carb time. You're 100% sure your carbs are set up correctly (although I'm a little less confident :)). Check for air leaks around the intake boots. This could make one or both sides lean, so lean they don't fire. Check for exhaust leaks. Sounds like you have one? Well, don't fuck with that until you do everything I wrote about earlier. Then fix it. A 72 has single wall pipes so you either have hole rusted through (doubt it), or late model double wall pipes with after market mufflers incorrectly clamped on, allowing exhaust to back flow out of the outer wall breather hole. Let us know. But NOT until you've done everything else!

Follow these steps to get 99% of XS's back on the road or diagnose what larger problem you have.

Cheers,
Adam
 
right so i have made an improvement on the running. compression was good (135 right 140 left). valves and timing were adjusted. timing was 3mm out. and I made doubly sure the carbs were clean air compressed and all. needles were set to no4 position from top as per manual, 3/4 turns out on the mix screw and fired her up. i also plugged the hole in the exhaust. left plug was a beautiful brown colour but the right was black and sooty. she made an improvement on the idle when i cut the fuel supply off so i lowered the needles to no 2 position. much better idle response from right but now the left is too lean and the right is still too rich. i have sprayed the manifolds for leaks with WD40 and no response. she is a lot better now than before but shes hestiating under load, im guessing thats because i dropped the needles, but if i raise them we are back to square one
apreciate the help you guys are giving me best regards
 
Is the right carb responding to the mixture screw now? If not, the seat may be damaged or you may have a defective float valve--a strong possibility if you bought anything besides a genuine Mikuni replacement.
 
Bike is running well on both cylinders but I'm getting no response from either mixture screw. Needle back to no 4 pos and I'm currently 2 1/4 turns out and I'm still too lean on both sides. I'm currently doing 10 mile runs then checking but each adjustment is no better. I'm also getting a little rattling from the top end which I'm assuming is overheating or cam chain adjusted badly. Any ideas on the mixture screw response. I may put the old float valves back in an see If there's any change. I have bought everything from Heiden tuning which is a European mikes xs without the high shipping and tax costs
 
Have you read www.amckayltd.com/carbguide.pdf ? If not you should. No response to the idle mix screw could be the idle circuits could be partially plugged.
Inexperienced carb cleaners often need at least several times of cleaning before they get everything clean. It took me about 6 tries on my own to get my carbs clean. This was before I found the carb guide. Now I can get it only after 1 or 2 tries.
Leo
 
Hi fellas. The problem has seemed to be fixed after the 10th time of cleaning however she's still a bit lean. Sometimes I think if you step back for a while and revisit after a week or so you get the best results. She drives like a charm. Had to grease the advance mechanism pins as the weights weren't returning properly. Thanks for all your help. I will however ask one more question. On the right hand carb the butterfly or the bit on the carb body that controls the throttle plate is a little wobbly. I'm guessing part of my problems stem from there. Is that fixable or will I be looking into a new carb set up?
 

Similar threads

Noidea
Throttle cable/idle adjustment vm34
2
Replies
24
Views
2K
AUTOMAN
A
L
Any Advice To Get This Engine Started?
Replies
18
Views
1K
jetmechmarty
jetmechmarty
devildrums
Tuning help needed
2
Replies
34
Views
2K
Paul Sutton
Paul Sutton
Optic Bliss
Only firing on right side, Is it Carbs or Points?
Replies
4
Views
661
Niels B
Niels B
L
Popping Noise After Carb Rebuild at Idle
Replies
13
Views
2K
Wingedwheel
Wingedwheel
Back
Top