gpz750 troubles....

jdreadrocker wrote:

Hi. I'm james and i'm new to the forum and here's my problem..I recently bought a 1982 gpz750 that looked like a good deal but now i think i've been had. The bike started and ran great when i looked at it but now that it is home i have only gotten the thing started one time and when i checked the pluggs they were coated in oil. I've cleaned the plugs just to see if it will even start again but all i get now is just a lot of noise and a backfire every now and then. I have been told that the motor will have to be rebuilt but i am really afraid of how much that is going to run me. if anyone else has had anything like this happen please let me know something and how you handled the situation. Any and all help is greatly appreciated. thanks,
james

If that truly is oil coating the plugs, the most likely place it is coming from is the valve guide seals. I just went through this on mine, the oil runs down the valve guide and leaks into the cylinder and ends up on the tip of the plug where it dries to a oily glaze which prevents the plug from firing. I would crank the heck out of it until the gas washed the plug clean enough to fire, then it would usually backfire a few times because it was flooded. valve seals are rubber and they do fail regularly.

FYI, the amount of oil that leaks into the cylinder is small and it leaks very slowly so you probably won't notice any blue smoke when running it. Sometimes you see just a bit at startup and then it's gone if the oil is coming from the valves. That's why sneaky weasels can slide this one past somebody who doesn't know it has the problem.

If your seals are toast, that would mean a head job, which would probably run about $300 machine shop labor and maybe $100 - $150 for parts (depends on if the valves are reusable). The big $$$ is the labor to take the head off and them reassemble it. If you can do it yourself, you can save that cost. if not, it might be another $400+ (I haven't priced shop labor in a while, maybe more).

bountyhunter thats what i'm afraid of. I have a guy that said he would take a look at it for me but it will be a couple of weeks before he can check it out. He has helped me before on another bike project and he's pretty good and spotting problems. I think if it turns out that the enggine needs head work then i think he can do it for a pretty reasonable price. At least i hope.

jdreadrocker wrote:

bountyhunter thats what i'm afraid of. I have a guy that said he would take a look at it for me but it will be a couple of weeks before he can check it out. He has helped me before on another bike project and he's pretty good and spotting problems. I think if it turns out that the engine needs head work then i think he can do it for a pretty reasonable price. At least i hope.

If it's a clean, low mileage bike you can think of it as an investment into a long time of good running. If you do a valve job, you should get the VITON rubber seals because they last longer than rubber. That will increase the number of miles until you have to do it again.

If somebody is going to give you a break on the labor, that's good. Most of the cost of the head job is labor. If he can lap the valves and install new seals, you can really get off cheap.

"If it's a clean, low mileage bike you
can think of it as an investment into
a long time of good running."

thats the way i see it but convincing my wife of that is a whole other story. it was hard enough to get her to consider me geting another bike in the first place. lol.

It would not be unheard of to find oil in the gas tank. When I picked up my LTD 750, the PO had coated the inside of the gas tank with oil for winter storage. I didn't notice this until I got the bike running (had only put a little bit of gas in at the time)and it fouled the plugs.

All it needed was fresh plugs, a quick clean of the carbs and a full gas tank (I figured it was easier to dilute the oil than flush the tank). Worked like a charm.

Good luck with the bike. These things are a blast to drive and work on.

AH HA! I think i might have run accross the problem...I was tinkering with the bike just checking here and there and cleaning it up. Well it has some k&n like air filters on the carbs so i decided to take them off and see how they looked from the inside...to my amazement when they came off oil poured out of them. They were all full of oil, not just a little to keep them from rusting...but enough to soak the ground. I cleaned them up and wiped off all the excess and cleaned the carbs a little, put some new plugs in it and within two pushes of the start button it was up and running! I hope thats the end of that problem. Thanks for all the help guys and gals!

well it has been a sad day today...and quite agrivating! I had the bike running like a champ, cleaned it up a bit, and even got to ride it around for a bit...yesterday. Today i go to start it and guess what! Nothing happens!:huh: The starter just starts making noise and the motor never fires or starts up. Aaaaaaaaaaaaaaaaa! This bike is going to drive me to insanity!

Don't go insane, yet! Though I, myself can't really help too much at this stage of my development/education, there are a bunch of guys here that can help you figure it out. Since you did get it to run and actually got to ride it some, it could be someting simple. Might be as simple as cleaning some electricals or such. Hang in there!