'72 GT550 running on all 3 cylinders? Video link included

[derekstudt]

This is my first post. I've been learning a ton on this site as I've been going through my first bike, a 1972 GT550J, and making sure it's as reliable as possible.

I'm posting this video of my 1972 Suzuki GT550 to see if anyone can tell me if it's running on all 3 cylinders or not.

I noticed yesterday that the left exhaust pipe is not hot to the touch after running. I have good spark. Battery is fully charged, and I just changed the spark plugs after recently fouling out the carb after the carb float sprung a leak. Carbs are clean and properly adjusted. Had I not had to fix the float, I don't when I would have noticed the lack of heat on that side of the exhaust.

No noticeable loss of performance or power. The only indicator I have to think it's not running on all 3 is that the exhaust pipe isn't hot. I'm hoping someone can tell from the sound if everything is ok. Any help is appreciated.

http://www.youtube.com/watch?v=J0DFRJ8sEOU

[Alan H]

Well, it's ticking over a tad high to be able to tell properly really, a well set up engine should tick over well below 1000rpm.
You say the exhaust pipe doesn't get hot. Does the exhaust get hot immediately where it joins the barrel? If it does, then the exhaust may be blocked after the joining pipes underneath so that the exhaust is shared by the two centre pipes and the right one. Possibly shitty baffle.
Put your hand behind each pipe with the engine running - can you feel the exhaust out of each pipe?
Does the engine sound change if you take the plug lead off the left cylinder does the tickover speed change?
If you rev the engine higher does the exhaust get hot?
Is the left barrel hot?

[bert0848]

I noticed the motor shut off when the key was still on. Mine acted much the same last year. I eventually realized it was not firing on the left. The gas would drip out through the pipe. My cause was the little insulator on the point was in the wrong spot, causing a short. Good luck on yours.

[derekstudt]

Well, it's ticking over a tad high to be able to tell properly really, a well set up engine should tick over well below 1000rpm.
You say the exhaust pipe doesn't get hot. Does the exhaust get hot immediately where it joins the barrel? If it does, then the exhaust may be blocked after the joining pipes underneath so that the exhaust is shared by the two centre pipes and the right one. Possibly shitty baffle.
Put your hand behind each pipe with the engine running - can you feel the exhaust out of each pipe?
Does the engine sound change if you take the plug lead off the left cylinder does the tickover speed change?
If you rev the engine higher does the exhaust get hot?
Is the left barrel hot?

Yeah, it was idling a little high in the video.

When I say the exhaust doesn't get hot, I meant up near where it bolts onto the cylinder, not after the junction.

I can feel exhaust coming out of the back of each pipe.

Thanks for the reply.

[derekstudt]

I noticed the motor shut off when the key was still on. Mine acted much the same last year. I eventually realized it was not firing on the left. The gas would drip out through the pipe. My cause was the little insulator on the point was in the wrong spot, causing a short. Good luck on yours.

I shut off with the key still on, because I killed it with the off switch...which couldn't be seen in the video.

I'm getting spark to the cylinder. I'll check to see if the insulator could be causing the problem, although my guess is it's not that, since yours was causing a short at the point. I would think I would be getting no spark if that was the culprit. Is my logic on the right track here?

[bert0848]

Since you have good spark, and the bike sounds okay, maybe check the thumb screw. That seems to also make a big difference on how hot the pipes are. If you can get an infrared thermometer you could use that to help dial it in. I would guess all three are firing since the tach isn't jumping to bad. But I'm still a beginner at all this too.

[pearljam724]

It definitely sounds like it's firing on all 3 to me. Bottom line, if it's not. It's extremely noticeable when you ride it down the road. It will run like a tird. The only time I have experienced a cylinder not firing is from a less than fully charged battery and using fine wire plugs. I like the how the bike runs when they are clean of oil residue. But, I have experienced that they foul very easily causing a cylinder not to fire if they are not. An easy test is to spray water on the header down tubes from a spray bottle after the bike has been running for several minutes. The pipe will sizzle if the cylinder is firing.

[Vintageman]

I assume you have nice spark, good compression in cylinder and checked the timing.

If fuel through pilot jet is plugged it will not fire when idling or small throttle opening.

However, if you driive down the road and use say 1/2 thottle or more then you should run off other jets and the pipe should get hot. Aslo the power should come on.

[derekstudt]

Hey Guys,
Sorry I've been MIA. Thanks for the replies since I've last been on the board. Vacation, work, summer with 3 kids, etc make for really busy times.

I wanted to give an update...

The bike has been running on all 3 cylinders. A friend of mine who used to race H1 triples said it wasn't uncommon for his triples to have 1 pipe run cooler than the other 2. They key was that I was having heat on all three pipes even if they weren't all the same amount of heat.

Judging by that, and the fact that there was no performance loss, I'd say it is fine.