Something Ugly

[Bert Patterson]

I just went to start my bike. Instantly, there was a loud pop from the left cylinder - where the pipe comes out. Now there's a little oil on the fins below it. I don't want to try to start it again.

Any ideas? This can't be good.

[Hap Call]

Re: Something Ugly

I just went to start my bike. Instantly, there was a loud pop from the left cylinder - where the pipe comes out. Now there's a little oil on the fins below it. I don't want to try to start it again.

Any ideas? This can't be good.

My first thought is that you have blown a head gasket. Pull the ignition cover, and all the spark plugs and slowly turn the motor over and see if you have anything binding. I want to make sure that there was no valve-to-piston interferance.

Hap

[Anonymous]

sounds like you had a cylinder full of gas, might have messed your head gasket up.

[Anonymous]

Sometimes my bike does this (less the oil). When it is warming up with choke I hear a bang and it stops dead in its tracks. Maybe you've got something non-lethal like me.

Steve

[Bert Patterson]

Thanks, folks. Well, here's the deal. Went to start it again and there was a loud detonation. Oil level was really high and gas was dripping from the carbs. Since the petcock is not set on prime, I'm guessing it's leaking like a sieve. It won't turn over now after the last bang and I'm hoping I didn't do anymore damage. Off to Bill's after work.

[Anonymous]

Depending on the state of your cam chain and tensioner, you can jump a tooth on the cam chain with these major backfires.

Check your cam timing to make sure it is still set on the right teeth.

Kim

[redliner1973]

Thanks, folks. Well, here's the deal. Went to start it again and there was a loud detonation. Oil level was really high and gas was dripping from the carbs. Since the petcock is not set on prime, I'm guessing it's leaking like a sieve. It won't turn over now after the last bang and I'm hoping I didn't do anymore damage. Off to Bill's after work.

Sound like your float valves leaked past filling the crankcase full of gas, and since all engines have some blowby, some ignited fuel went past teh cyl wall, into the crankcase which was full of fuel and fumes, igniting them causing your 'bang' Drain the oil and don't leave the 'cock on 'prime', put it to 'on' position. :twisted:

[Bert Patterson]

Sound like your float valves leaked past filling the crankcase full of gas, and since all engines have some blowby, some ignited fuel went past teh cyl wall, into the crankcase which was full of fuel and fumes, igniting them causing your 'bang' Drain the oil and don't leave the '#### on 'prime', put it to 'on' position. :twisted:

Thanks. It wasn't on 'prime', so I think I've got a leaky petcock.

[daveo]

It may also lock up the piston with gas, did you turn your ignition on then off, without using the starter? Sometimes if you turn the bike on and energize the coils, and then shut it off , the primary field in the coil collapses causing the secondary to spark, if a valve is open and fuel mix is right they can backfire out intake or exhaust, I've had it blow carbs off.

[skip]

Thanks, folks. Well, here's the deal. Went to start it again and there was a loud detonation. Oil level was really high and gas was dripping from the carbs. Since the petcock is not set on prime, I'm guessing it's leaking like a sieve. It won't turn over now after the last bang and I'm hoping I didn't do anymore damage. Off to Bill's after work.

sounds like its hydrolocked with gas youll have to drain the oil and probably replace petcock. Ive been using a pingle petcock for years. Its the dual line one, I need the extra fuel line for the nitrous system but its been great for 15 years now.

[Billy Ricks]

Bert,

If you haven't already seen my posts on how to adjust the petcock here it is again. I've had mine leak before on a couple of occasions and I'm always able to cure the problem by making an adjustment.

The diaphram has a spring on the right side towards the motor that returns the diaphram to a position where no fuel flows if there is no vacuum or the petcock is off the prime position. On the left outer side of the diaphram is a rod that is acted on by the petcock lever. It is on the other side of the plastic valve from the lever. That flat metal rod has a loop of spring built into it. You can stop your leak by varying the length of that rod simply by shortening or lengthening the spring portion of the rod. Sounds like yours needs to be shortened. When you disassemble the lever portion of the petcock pull everything straight out so you don't mangle that rod. You know you have it right when you get no fuel flow in the run positions with no vacuum and flow on prime. Check to make sure you get good flow with vacuum applied. You can run a line into a bottle to watch fuel flow while applying vacuum.

[Bert Patterson]

Thanks folks. Everything's fine now. The petcock was shot - near impossible to move to reserve or prime and just pouring gas. Dripping from the carbs. Cylinder #2 was loaded with gas - hydrolocked.
New petcock, filter, fluid, plugs, we're cool. And a new front, because, well, it was on since last June and that's pretty damn long.

When I buy my Aprilia, I can start learning to do a little work on the GS. The Yamarat - I'm too spoiled to ride - and the airhead's been in need of carbs forever. Need two proper bikes.

[earlfor]

So Bert, youre getting Aprilla? Whatcha gettin?

Earl

When I buy my Aprilia, I can start learning to do a little work on the GS. The Yamarat - I'm too spoiled to ride - and the airhead's been in need of carbs forever. Need two proper bikes.

[Bert Patterson]

So Bert, youre getting Aprilla? Whatcha gettin?

Earl

That's the plan, but not until at least late summer. At this point it's really a struggle between a Mille and Falco. An R would be coolest, but I'm really not good enough to benefit that greatly from an R. The Falco and Mille are pretty similar to me - the Falco's more relaxed, but the Mille is definitely not uncomfortable. And actually the Falco is sporty enough for me. I'll be looking used first from the Corse Cafe north of Milwaukee - he gets a lot of beautiful bikes and is very generous about tossing you the keys.

Oddly, I'm kind of cross-shopping with the Triumph Daytona (Ducati's too much of a commitment). Mille and the Daytona are really sweet sportbikes on the road, unique tough motors and they pull like a D10.

[earlfor]

Sounds great. I would love to have a Ducati or an Aprilla, Triumph etc. but my problem down south is any kind of parts or service is nonexistant.

Earl

Oddly, I'm kind of cross-shopping with the Triumph Daytona (Ducati's too much of a commitment). Mille and the Daytona are really sweet sportbikes on the road, unique tough motors and they pull like a D10.