79 gs850 troubles PLEASE HELP!!!!

[faderox]

I recently purchased a 79 gs850 and it runs great for about 15 minutes or so and then it begins to backfire and hesitate. I am not a very experienced motorcycle person and I would love any help that can be given. I have tried a number of things including replacing the following items: air filter, spark plugs, and coils. I have had the timing adjusted and I am now in the process of cleaning my carbs which is a project that may be beyond my capabilities. After replacing the coils I took it for a ride and accelerated to 80mph very quickly then I ran about 70 mph for 15 minutes before it started acting up. Please somebody give me some suggestions on what to check next. I have had this bike since it was too cold to ride and now summer is almost over and I still have not been able to ride it.

[pete]

I'm nowhere near a guru or anything like that, but one thing to try is popping the fuel cap, it's possible the breather hole has been plugged up at some point, which will eventually cause the carbs to starve of fuel.

[BassCliff]

Greetings and Salutations!!!

Hi Mr. faderox,

It could be something simple, like a non-venting gas cap (which must be disassembled and cleaned) or a plugged filler neck hole (possible if the fuel tank has been lined) but it is probably a combination of things (dirty carbs, faulty intake boots and O-rings, etc) which can only be remedied by going through the maintenance lists in your "mega-welcome". Take no shortcuts or you will be frustrated and will probably never ride that bike much. Take the time, and the money, to do all the proper maintenance up front or it will never run right. It's a 30 year old machine and needs a lot of TLC.

Anyway, to get you started, let me point you in the right direction, dump a TON if information on you, and share some GS850G lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. Now let me roll out the welcome mat for you...



Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[kmontague]

totally agree. i did all the stuff in the list and my 78 750 runs GREAT!!!!

[Big T]

It needs new points and condensors

The condensors are heating up and failing

[BassCliff]

Hi,

It needs new points and condensors

The condensors are heating up and failing

Yes, this is reasonable. Points and condensers are cheap. Do the rest of the maintenance too.

Thank you for your indulgence,

BassCliff

[silverhorse47]

I think replacing the parts you replaced sounds reasonable, and will do no harm. However, if it were a coil going wrong, which overheating 'can' cause, it is probable that you'd be describing the condition as 'misfiring', not 'backfiring'. You do not mention ambient temperature in your post, but it usually takes a bit longer that fifteen minutes for frame mounted coils to get hot, so .... I doubt it.

Were your plugs black powdered up black when you replaced them? Or were they white?

The engine can 'backfire' through the carbs, or through the mufflers. I'm going to assume that your bike is backfiring through the mufflers.

If this is the case, after your bike is warmed up, (and what you are describing in terms of riding the bike is a very rapid warm up which probably doesn't even get the oil up to temp...imo ... which may actually read 'cold' to the coils) so the poor engine may be exhausting cold unburnt fuel into a burning hot exhaust system, and glowing hot stuff in the outlet pipes of the bike is firing the fumes out the back end as a back fire.

The exhaust system of an internal combustion engine is very hot. If the engine sucks raw fuel or fumes into that hot tube...the engine is going to backfire.

I would like to hear what happens if you just drive the bike at normal speeds, gently and easily, for say half an hour, then slowly over the next half hour, open it up?

If your plugs were tan/brown, your air cleaner was new and not all oiled to death and your coils were new....and your float circuits prove to be intact and not bleeding fuel....maybe you should look at your ignition circuit.

<---not a guru, either.

[faderox]

thanks

I am greatful for all of the advice. It looks like I have a lot of work to do. Keep the suggestions coming, I will try just about anything at this point.