Timing belts replaced, now won't run under 2000 RPM

[mmstingray]

So there ya go. I checked all the plugs and there all brownish-tan. I would ordinarily suspect wet wires or something, but it doesn't backfire and it seems to be firing on all cylinders. All i know is that it very abruptly shuts off at 2 grand. I get so close to having this bike as it should be, then something immediately bites me in the ass. I changed belts as a matter of course because I didn't know their age.

[mmstingray]

Man, what a day.

Okay, I got it to run at under 2 grand. Now I'll be motoring along, dump the throttle, then roll off and cruise, and then the power disappears completely. Not like a mixurte problem, but like both the gas and spark on all cylinders completely disappear. It comes back after a few seconds, but the dropout is almost violent. I'm too spent to even troubleshoot the thing any further today.

[rcmatt007]

question: did it run okay before the change? if it did, then soemthing went wrong with the change... maybe you are a tooth off... will run but not quite right....

some thoughts

[mmstingray]

It did run okay before the belt change.

After replacing the belts, i cranked it by hand using the kick starter many times. I then ran the bike for approximately 30 seconds with the choke on and it seemed to be doing just fine. That's when i realized I had oil spewing out of the flywheel viewing hole. I then shut it off, sprayed it with degreaser, and hosed it off. I ran it immediately thereafter once again with the choke on, and it seemed to be fine. But once i got to about 1/3 choke, it just shut off.

I hit the whole engine with compressed air, and then took it for a ride. After the ride, it ran fine below 2k. It still was kind of a lumpy idle, but it always kind of had that once it was fully warmed up anyway. I took a stab at synching the carbs, not completely pleased with the results, but satisfied enough that it was running reasonably well and that I could sort out the fine tuning at a later time.

So then I went for another ride. It didn't quite have the snap it should, but I assumed it was because of a rushed synch job. Then I'd dump the throttle, it'd take off strongly, get up to about 8 grand and the power would just disappear like I hit the kill switch (which never came in contact with water), then returning in pulses and running fine in lower RPMs.

If it were a tooth off, wouldn't it be at least backfiring or something? I had all the marks aligned perfectly, so I can't imagine what I could have done wrong. The belt tension(s) was also fine finally.

[rcmatt007]

a tooth off will just make it run loosey.... it would be just be a weeee bit off.... anyway, if it ran good before, I would just wonder if that was where the problem was...

song on the radio... this time lor you gave me a mountain.... a mountain a might not climb...you gave me a mountain this ime

sorryy... listen to old C&W stuff

[mmstingray]

There was one curious thing I just remembered:

After hosing it off, I turned off the engine. From the left rack of carbs, I could hear a sucking sound. I couldn't tell which one it was, bur I've never heard it do that before.

[shatle]

It did run okay before the belt change.

If it were a tooth off, wouldn't it be at least backfiring or something? I had all the marks aligned perfectly, so I can't imagine what I could have done wrong. The belt tension(s) was also fine finally.

Have you gone in and re-checked the timing? I didn't realize it, but even when you align the marks "perfectly" it can still throw the points off. I was amazed at how much better my bike ran after I re-timed it after changing the timing belts. It ran OK after the belt change, but it was advanced once I went in and checked. After re-timing it was smooth as silk.

Hope that helps,

Steve

[mmstingray]

No Steve, I haven't done that yet and it's an excellent idea. I have electronic ignition (previous owner put it in and I don't even know who makes it), and it just looks so...non user-serviceable. But I have never been able to get those carbs synched right. I have analog synch gauges, and they're just horrible.

The sudden disappearance of power is especially baffling, tho'.

[shatle]

The sudden disappearance of power is especially baffling, tho'.

I agree- it seems unlikely, but then again if it was easy you would have already figured it out I guess it can't hurt to check. I believe the method of checking the timing is the same- you just don't have to worry about the point gap, etc.

Let us know how it goes.

Steve

[Frenchy]

I would recheck the timing marks on the belts!! If the left bank's out & you rack into it, it can throw the timing way out with the mechanical advance.....

As for the sucking sound: Was it with the motor wet from you hosing it off???
It not: With the bike running, spray starting fluid around the carbs & intakes.. If she revs up, you've found the leak....

[octane]

...I was amazed at how much better my bike ran after I re-timed it after changing the timing belts. It ran OK after the belt change, but it was advanced once I went in and checked. After re-timing it was smooth as silk....

I remember Randakk mentioning that changing the belts can
throw off the ignition timing simply cause you replace a
set of old , as in ;sloppy and slightly LONGER belts.
...with a set of fine new and therefore slightly SHORTER belt.

The length difference (and we are talking small difference here obviously)
will off cause change the timing (again; small things, but aparently enough to feel a difference)

[mmstingray]

I know Randakk sells one, but where does one find the tool (the light thing) for static timing? Is there something that can be improvised at home?

[shatle]

I know Randakk sells one, but where does one find the tool (the light thing) for static timing? Is there something that can be improvised at home?

Two pieces of wire with alligator clips at one end and soldered to the socket for a 12 volt automotive bulb will do the trick. You need the bulb in there, too

You can get continuity checkers at an auto parts store for a couple of bucks. Be sure to get the one that doesn't come with a battery in it- get the plain one since you want the bike to "light the light" not the battery in the checker.

Does that make sense?

[mmstingray]

Perfect sense, shatle. Thanks! It'll be nice to not have to spend a mint on something for this bike finally.

[rcmatt007]

I always used a left over turnsignal light with the clip on the wire and set the body on the engine