First Bike, 1977 GT500, It might be a bit of work.

[22Garnet22]

Hi everyone,

As way of introduction, I just passed the motorcycle safety course and I am now able to ride a motorcycle. Preferably wanting to get practice in before the end of season, I have been actively looking around for older, cheaper bikes. My dad just restored his '71 H1 kawasaki triple and it got my fingers itchin'. Anyways, I came across a '77 GT500 and it looks to be in decent condition for it's age and only has 7760 miles on it (6 miles since the safety three years ago). We fired it up today and found that it is only firing out of 1 cylinder, although it still starts fine, and I was wondering if anyone here might know of a possible cause for this. My dad and I are going to (hopefully) run a compression test soon to see if the rings are working fine. He's saying it might be something simple because of the low overall mileage and the low mileage put on since the safety would hopefully not be enough to cause any major malfunctions with the bike. But who really knows. If anyone has got any ideas or had similar problems, it would be much appreciated.

P.S.
Does anyone know how to get a hold of a service manual for a '77 GT500, either online or some other source?

Much thanks,
Garnet

[diamondj]

Hey Garnet,

The GT500 is a revision of the T500 produced from 1968 to 1975. In 1976 they added an electronic ignition and a disc brake on the front. They updated the tank and some other cosmetics and renamed it the GT500. So technically it doesn't have it's own service manual. There is a GT500 addition to the T500 factory manual that you can download here:

viewtopic.php?f=19&t=151

Jim

[Coyote]

If it's the left cylinder (as seated on the bike), the most likely cause is a low battery. I am not a 500 owner, but from what I have read over the years, they will always drop the left when the battery is low. This pertained to the T500. Since your GT500 has an electronic ignition, this may not pertain to your bike.
p.s. We like pics! Oh, and welcome to the message board!

[titan performance]

Plus 1 with what Coyote has said re a low battery, but if it's not that, then check the spark plug and cap. The Gt has only 1 coil, with a wasted spark system firing both cylinders, so it's unlikely to be electrical other than the battery, plug, or a shorting ht lead/cap.

[22Garnet22]

Excellent link for the manual Jim. Saves me some grief trying to track down the manual.
It's actually the right cylinder that isn't firing. I haven't bought the bike yet so I don't have any pics that I've taken but here's the pics the owner put up. I'm probably going to buy it quite soon because I've got the manual now (thanks again Jim) and I am can't wait to start working on it. The owner actually replaced the battery so bonus points there.

http://winnipeg.kijiji.ca/c-ViewAdLarge ... =288936576" onclick="window.open(this.href);return false;"

Thanks for the help so far guys, might help put me out on the road before the snow falls!
Garnet

EDIT:
Oh and except for the tail light and I think a couple other parts, it is all original. The guy bought it for that reason in the first place but apparently doesn't have enough time for it due to his other bikes.

[22Garnet22]

Hey guys, my dad was wondering since he focuses on kawasaki triples, if $700 seems like a good price for the bike.
Some things to note would be that he replaced the tires and the sprockets and chain for the safety, he replaced the rubbers for the carb intakes and a new gas cap.
There is however some spot rust and surface rust on some of the chrome but it looks like nothing integral or major.

Thanks again,
Garnet

[Coyote]

$700 is a steal in my opinion for one that clean and straight. New gas cap = $100. New tires, chain and sprockets = $300+. New battery and intake boots is at least another $100 plus. Grab it NOW!

[titan performance]

You boys across the pond are spoiled.......we couldn't buy that bike for 700 gbp !
1400 gbp maybe.

[22Garnet22]

Hahaa that's what I thought. I'm pretty sure I'm buying it in the next couple of days so I can hopefully get some work done on it.
I'll let you guys know what happens.

[Scorch]

That appears to be a steal, really nice bike. Look forward to hearing about your work on it.

[22Garnet22]

Alright! Got the bike. Bought it this afternoon and just did some fiddling with the plugs and such. We swapped the plug leads and still the left cylinder is the only one firing, both plugs spark and the right one is wet with fuel and we swapped the plugs and still just the left fires. The plugs are OK, the plug leads are OK, and the right cylinder is getting fuel so we're going to have to delve deeper. We ran a compression test and both cylinders were ~130 psi so that's alright. There is some gas leaks from both the overflow tubes but my dad said it probably wouldn't be related to the right cylinder not firing. Just more work to be done later.
So I'm totally excited to have this bike, looks awesome, feels like it fits and is gonna be a great experience. If anyones got any troubleshooting ideas I'd love to hear 'em.

Proud new owner,
Garnet

[wvc]

have you held the plug against the head while turning over the motor, to be sure you're getting a nice fat blue spark on that cylinder? if you have a good spark, then it is either a fuel or compression problem. If theres no spark, I would look closer at the leads, maybe swap in another coil. Since you've already swapped plugs, the spark plug I assume is good. Try unscrewing the the plug boot off the lead, the snip off 1/4" or so of the lead to expose new wire, then screw the boot back on. Let us know what you find out.

[tz375]

Congrats on that new bike. It looks good from what we can see.

Weeping carb and wet plug tends to suggest a crankcase full of fuel on the right side.

Take the right plug out and spin the motor over by pushing it in gear or kicking it with a rag over the plug hole to catch the spray.

Or you could try to remove that carb and wriggle a tube down to suction out surplus fuel

Or just take out the drain plugs and let both sides drain out.

Remove both carbs and clean and adjust the floats as required. Dripping gas and hot exhausts can be a nasty combination.

Then drain the tank of gas and put that in your car/truck and fill with fresh gas.

Insert new plugs and have fun.

[diamondj]

Or just take out the drain plugs and let both sides drain out..

I think I remember reading Suzuki eventually got rid of the drain bolts under the crankcases but I could be wrong.

Look under the engine and if you still have the cylinder drains, there will be a bolt head directly under the center of the cylinder bore on each side of the engine. They will not have the Suzuki "S" cast into them and you'll get some oil and gas mixed draining out when you remove them.

I'd also recommend checking the carbs again to make sure you don't have a leaking float or a worn out needle jet (the springy thing under the float). In fact, replacing the needle jet and seat is probably a good idea anyway.

Pat's Small Engine has decent deals on Mikuni parts and you can get Viton tipped needles and seats for not a lot of money:

http://www.psep.biz/store/mikuni_needle_seat.htm

Part number ADVM2851125 which is a size 2.5 and has the Viton tip should do the trick for you. Or if you prefer the metal tipped needle it's part ADVM2816325.

Jim

[Coyote]

That was my first thought Jim. A sunken float. And yes Garnet, replace the float needles as Jim suggested. It's amazing that something the size of a small pill plays such a major role in fuel control.