please help me!!!!!

[greatwhiteshark]

I'll make this as short as possible
bike is a 1980 xs1100 special 35,000 kms. P.O. had it sitting in his garage for 6 to 7 years . When I bought it it was only running on what seemed 3 cylinders it popped and backfired through the right side exhaust very badly . Took it into local bike shop they took off the carbs cleaned them replaced float valves put it all back together . It ran much better but still popped and backfired on right side at Idle as well as when revving .they told me it was the valves probably needed to be adjusted so they did that but it made no difference. then they suspected burnt valve so they did a compression test there was variance but it was within specs they also did a leak test wich checked out .So they said it was not a burnt valve and then figured it was some corrosion in one of the carb bodys air holes . So they said if we had some other carb bodys we could put all the parts from these carbs into those ones, well I happened to have an extra set of carbs at home so I brought them in and they cleaned them and did the swap and told me that they made no difference. But when I went into the shop to check it out it no longer popped and backfired at idle or when revving but if you revved it up to about 3000 to 4000 rpm's and held it there it would backfire quite a bit the higher the rpm's the more it would backfire not big boomers more like a machine gun kind of backfiring out the exhaust . So now they are saying they think it is a burnt or sticky valve that only malfunctions at higher rpm's I think this is a cop out and they don't know the problem and don't want to spend any more time on it . Now I am not a mechanic , but I have learned quite a bit in a short time thanks to this site , but right now I am in need of some serious help, this situation is begining to drag out and become very frustrating and expensive does anyone have any ideas . they also say they have checked the coils by changing the plug wires around also the exhaust is not in great shape and does have some leaks but I think this would only cause backfiring upon deccelaration....any and all help would be greatly appreciated ......thank you ...mark

[TonimusMaximus]

Have you checked the temperature of each pipe to see if one is a lot less than the other? Maybe you've got some sort of exhaust leak. Odd problem.

[Shuriken]

I think the shop does not know what they are doing. It sounds like they are just throwing out blind theories.

How does the bike run under power? Does it sputter and pop when driving it?

The carbs have to be perfectly tuned to eachother if you want the bike to run right. The float height has to be spec for the year of your bike. The jetting should all be set to stock and adjusted from there based on altitude. All of the carb passageways should be clean and free gunk. Once all of that is correct the carbs should be synchronized - very important.

My experience with sputtering problems has nearly always been electrical. Sometimes a cylinder goes dead and it's easy to blame a coil - when changing the spark plug solves the problem.

I had real problems with sputtering and found out I had bad pick up coil wires. Fixing them solved a lot of my problems.

Most recently I've had trouble with the bike sputtering and even dying because of a faulty ignition module - the black box under the seat. A proper resoldering job fixes this problem.

If your carbs are set up correctly and are synchronized, and the pickup wires are fine and the bike has new plugs, what would happen?

I doubt it's a valve problem.

Ben

[MartyA]

Yeah, run from that shop. Bring your bike with you.

You said they cleaned the carbs - did they triple clean them? You swapped another bank, were THOSE triple cleaned. Gas can leave varnish deposits in as litle as two months. There are little holes in there that the gas has to pass through, a little varnish can interrupt that flow. Clean them again, be sure the correct jets are in, no tips broken off, etc., and be sure the carbs are at least bench synch'ed.

I agree with Ben, though, almost sounds electrical. When you rev the motor, the vacuum advance pulls on the coil pick-up wires. They tend to break over time, causing intermittant sparking. Check for the hourglass shape in the insulation when you gently pull on the coil wires. Be sure the vacuum hose to the advance is connected to #2 carb, not the carb boot. Look for any wires rubbing or loose - including plug wires.

Check the valve clearance also.

Fix those exhaust leaks, or try sealing them to test that as a problem. Check for blockage in the exhaust - laugh if you want but I found a couple of acorns in my muffler the first spring after I stored the bike for the winter.

Do you know the compression test results?

[mitch]

Thread

Hey Great white go back and read thru your origional thread on this subject your answer to your plea was given to you back there . You have a fellow living close to you that would for sure help you out if you asked him just send him a private message. I bet he could have it running in no time. My bet is its the pick up wires or the carbs, just cause they work on bikes dosent mean they know how to fix 25 yr old ones ! When you get it running right you are gonna love it. .................................MITCH

[TopCatGr58]

Hey there Great White,

I've got an 81SH, rebuilt the topend, new pistons, rings, valve job, and cleaned my carbs the best I could....but has frozen pilot jets and could not get out, did not want to bother with attempting to drill out/easy out and possibly bung up the ONLY set of carbs I have, so I cleaned as best I could. I also haven't replaced my exhaust header gaskets(YET!) and so I'm sure I've got a little leakage there. My bike runs strong and great under load and will idle after warms up. But if I just hold the revs at 4-5k, it, too pops a bit. It also pops upon decel, but it's done that essentially since I put my 4-1 pipes on many years ago, and now also with my Indy filters even after rejetting to correct a lean situation. The carbs have only been bench synched due to the less than perfect idle circuit, but it runs great for me otherwise, and I've driven several thousands of miles in rallies and such. These bikes are 20+ years old, and so I don't expect it to run and behave perfectly, like it was brand new!!!

SO..I guess what I'm saying is something along the lines of perhaps setting more REALISTIC expectations on the bike's engine and performance. But getting help from a local XSive can go a long way also!!
T.C.

[ratbyk]

Help!

Tim, here are my suggestions as possibilities:
1. Diaphragm spring left out of one carb not allowing all 4 diaphragm pistons to rise and fall equally.
2. Bent or misaligned needle in one carb causing the same affect as previous suggestion.
3. Vacuum advance hose not on correct nipple on #2 carburetor.
4. Hole in vacuum advance diaphragm not allowing it to advance and follow changes in throttle openings.
5. Centrifugal advance seized and not following the engine RPM up and down properly.
6. Pickup coil wire broken and interrupting the ignition spark intermittently.
Ken/Sooke
78E Ratbyk
83 FT500 "lilRat"

[Jeff]

If it were snapping and popping from one side at lower RPM.... I would look first at carburation.... mainly either a plugged or restricted idle jet or plugged up emulsion tube holes. Most low to mid rpm problems seem to come from dirty carbs.

Since it is doing it at higher RPM.... I would probably start looking at the centrifugal and vacuum advance mechanism to ensure it is working smoothly with no binding.... that the vac advance hose is connected to the proper port and definately at the flexible pickup leads.

[dragxs11]

Well you don't really have to listen to be, but I'd be willing to bet a decent amount of money that I know whats wrong. Your bike is fairly young in miles, so I'd step away from the pickup coil wires. Ignition coils very rarely go bad, but they get picked on cuz electricity is the black sheep when problems elude people. Valves will do things like you describe, but it doesn't sound like your engine has been abused...........After sitting for 7 years your carbs will give you terrible headaches. The pilot and main jets primarily. I agree with those who have said it. Clean the heck out of those things.
Matt

[Redbaron]

Popping at higher speeds

DragXs11,
To quote you " you don't have to listen to us" but, the coil pick up fix has absoulety nothing to do with a bad coil, it has to do with a broken or loose wire coming from the reluctor pickups at the closest thing we have to a distributor. In this situation the coils would be fine but unable to complete the circuit to fire. I would look for faulty wiring before I'd look to a faulty coil. However if you wish to check your coils easily there are several articles here on just how to do that and alleviate any questions. As I mentioned in another reply an Ohm Meter is priceless and required for this test. If you can't find the info here e-mail me and I'll send you the resistance values from my Haynes Manual. Once you have the tank off this takes about two minutes and eliminates a lot of guess work. IMHO

[Redbaron]

TO:Great White Shark

I don't mean Drags is wrong but if you read the current threads you will find many people who found great joy by simply repairing a frayed or broken pick-up coil wire. If the shop did a proper valve job and you problem is only at higher speeds I'd look to other causes. First and foremost take your bike home now, more bikes have been ruined by "parts changers" and wild a** guesses than by owners. If you test and find no problems at the pick coils try this: (quick and painless) have someone rev the bike up to the proper RPM's to recreate the problem. Then back out on the adjusting screw at each carb 1/2 turn at a time until it goes away, should not take more than 1 full turn if bike runs anywhere near properly. This is usually caused by a lean condition, and to give Drags his props, improperly cleaned or re-built carbs. I had this problem and the guy's here directed me as I am advising you. My snap, crackle, pop was repaired in just the way I described. But 25+ year old wiring is not to be trusted under any circumstances, check it first.

[Targetman]

My bike has around the same mileage \ and the pick up wires have been repaired three times, once by me, looks like twice by P.O.

[dragxs11]

So what happened to Mark? I'm curious as to what he has found out. In reference to my own bikes, I had no pickup coil problems till around 55,000 miles on one, and still going at 40,000 and 22,000 on the other two. Just lucky I guess. And my carbs on the second were, as suspected, my problem. As far as the relationship between the pickup coils and ignition coils, perhaps it was not clear that I was talking about two seperate suspected problems. Still I can only speculate being that I can't see or hear Marks bike in person. Just shooting at odds from my own meandering experience.
Matt