bike is stumbling

[3Phase]

so far its only under heavy load in second gear. as im powering through second it makes a strange pop as it stumbles. thats the only reason i dont thinks its a drive train issue.

i feel that the hight end stumble/starvation feeling is mostly the carbs and hopefully the pick up coil fix will dial that.

I can't remember but have you cleaned the pod filters, set the valve clearance and done a compression check?

could the pick up coil issue cause that hard stumble or does it feel more like the light clutch slip/lean carb stumble?

I don't know. I haven't had the bad pickup coil wire problem so I don't know what it feels like, I've just read about it.

If your bike just started doing this when you changed the main jets it could be a loose/cracked main jet or a missing/incorrect washer under a main jet.

Check and clean the inlet bell air jets and find out what size pilot fuel jets you have; check the slides to make sure they don't stick in their bores and the slide diaphragms don't have any pinholes in them; double-check the float bowl levels before you button the carburetors back up.

If it's been doing it for a while it could be all of the above, plus: dirty/bad pod filters; weak diaphragm springs; worn jet needles and needle jets; start enrichener jets leaking; bad ignition timing; bad grounds; bad coils; bad coil wires; bad spark plug boots; bad spark plugs; bad ballast resistor; bad wiring harness connections; bad ignition switch; bad fuses; bad fuse box clips; low system voltage;bad battery; bad TCI.

I havent checked the other jets, but i did put the 117.5s in the middle two and the 112.5s in the outer. still need to resync though to see how she is really feeling. she's pullin like a beast with the new clutch though. now i just need to figure out this new damn issue.

Don't worry about carburetor sync and mixture screw settings too much while you're tuning the top end at Wide Open Throttle (WOT). You need to adjust the valves, then do a compression test to see if the compression readings are even across all four cylinders.

After determining the mechanical state of the engine you have to be certain that the ignition and the charging circuits are working 100% before you even begin to try to tune the carburetors and the exhaust.

Take your time and don't try to skip steps or rush anything.


Regards,

Scott

[soulrydemike]

I can't remember but have you cleaned the pod filters, set the valve clearance and done a compression check?

no i havent, i wouldnt know how to. its my first bike and im learning everything along the way. i havent done anything to the engine at all. all ive done is got her running as smooth as i could so far with redoing the carbs, new fuses, fuel lines, brakes, battery, and oil. I want to get into dialing in the engine but i dont know where to start and cant afford to pay a shop to do it.

[soulrydemike]

I am guessing you are in the very early stages of second gear going south. Not a big deal to fix.

whats the easiest way to fix that.

[bikerphil]

Transmission repair tech tip...

http://www.xs11.com/xs11-info/tech-t...lwalkthru.html

[3Phase]

You need a manual

no i havent, i wouldnt know how to. its my first bike and im learning everything along the way.

Mike, that's no problem. The bike felt great when I rode it but I didn't hammer it around Garth's apartment and his neighbors and I didn't even try to go WOT because your clutch was bad. The seat of my pants says it's in great shape but you need to check it to make sure it really is in great shape and that it stays in great shape instead of becoming a parts bike.

What you need now is a fine manual. (I know, it's cheating if you read the fine manual....) If you don't have a fine manual to read -- stop working on the carburetors and fuses and fuel lines and battery and brakes and oil and mufflers and go get a fine manual and read it!

Garth might loan you his manual if you give him the $8000.00 deposit he had to pay Yamaha in advance just to order it or you can download a computer-readable PDF version from CatatonicBug's website:

My Bike

When you check the valve clearance, make sure you use the specs for the correct year of the engine you are checking. You have a 1979 engine so you would use the 1979 valve specs:

Exhaust valve clearance (cold) = 0.21 to 0.25mm (0.008 to 0.010 in)
Intake valve clearance (cold) = 0.16 to 0.20mm (0.006 to 0.008")

After you have checked the valves, check the compression. If you skip what seems to be a boring, overly complicated, technical, complete waste of time you can make a check and adjustment turn into a time consuming, expensive, repair or you could waste hours, days, weeks, or months trying to fine tune around valves that are a little too tight, a little too loose, leaking a little bit, or a piston or two with worn, stuck or cracked rings.

Have fun and take breaks when you need to. If you get stuck, give me a call or post on the forum here and someone will help you out!


Regards,

Scott

[DGXSER]

I'll secodn the valve check. Just last weekend a group of local members gathered to help look over another members "new to me" engine and check valve clearances. Wound up he had a bent intake valve.

Not to hard of a fix, but still, without finding that we could have spent months trying to get it to run right.

Oh yeah, do get the manual and then go through the entire maintenance section and perform all of those task, a couple each weekend or so. AND before you do them, check the tech tips here to be sure there is not a known issue with how Yamaha tells you to do it that has been corrected or amended here.

[soulrydemike]

the journey just never seems to end with these things.

Scott- thanks for the great tips man. I downloaded the digital manual and have begun the journey through it. Garth is cruisin by friday to help with a few things and if we have time , im gonna try to get him to help me with the the valves. she is running strong though. as long as i dont push to XSively she doesnt kick out that stumble. i do however want to track it down though so it doesnt turn into a huge mess.

dgxer- great point on running through all the maintenance checks. I guess i should have thought of that one first.

Im pretty sure this site is more helpful than the manual or anything yamaha has out there. thanks everyone for being such a great help.