help! wont start hot

[robz27]

new bike 1981gs 550. also new to forum. confident I will find some help.
just purchased bike. starts cold great runs and accepts trottle well.
however it wont refire once up to temp.
what I have checked up to this point.
visually checked spark cold and when hot/not starting. looks like same stength of spark.
when engine is hot and wont start,checked plugs. dry as a bone. However it will start off ether and continiue to run off gas.
I removed gas tank and made a gravity fed make shift fuel bottle to bypass vaccum operated petcock concerns. still wont refire once engine is hot.
The real kicker that has me stumped, engine hot. wont start. UNLESS I push/bumpstart. once push start runs like a champ

[Ranger]

So it starts extremely well when cold? Choke on when cold?

[BassCliff]

Greetings and Salutations!!

Hi Mr. robz27,

It sounds like it gets lean once it's warmed up. Probably due to leaks in the air intake system. Here, take one of these and call me in the morning....

Let me dump a TON of information on you (click the links below) and share some GS 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 Rebuild Series, and the Stator Papers. All of these issues must be addressed in order to have a safe and 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

[Nessism]

Have you checked the valve adjustment yet?

[Whitedog]

Had the same issue with my 550 last summer, after a valve adjustment and carb cleaning and tune. Spark hot or cold. Would bump start fine hot.

Turned out to be a weak battery. With plugs out starter would spin free and bike had spark, with plug in starter needed more juice to turn engine, ignighters would not have enough juice to fire plugs. (no relay mod yet)

New battery and no problems since.

[robz27]

yes, it starts correctly when cold with choke . choke seems to operate as it should

[robz27]

Had the same issue with my 550 last summer, after a valve adjustment and carb cleaning and tune. Spark hot or cold. Would bump start fine hot.

Turned out to be a weak battery. With plugs out starter would spin free and bike had spark, with plug in starter needed more juice to turn engine, ignighters would not have enough juice to fire plugs. (no relay mod yet)

New battery and no problems since.

when bike is hot in the non start mode i put charger on boost. wouldnt that rule out weak battery?

[robz27]

still troubleshooting

looks like newer valve cover gaskets and new style allen bolts on intake boots. after reading about valve adjustment on bikecliffs site, not sure i want to fly into that project. Im still not sure what else to check? I did spray ether around intake boots. no increase in rpm. still stumped that it will bumpstart and run perfect once started

[Nessism]

looks like newer valve cover gaskets and new style allen bolts on intake boots. after reading about valve adjustment on bikecliffs site, not sure i want to fly into that project. Im still not sure what else to check? I did spray ether around intake boots. no increase in rpm. still stumped that it will bumpstart and run perfect once started

Run the bike until the valves burn up? It's stupid to try to diagnose a bike when even the basic maintenance is not performed.

[DanTheMan]

Do your valve shims! It's not that hard, and the bike will then start when hot. You'll be amazed! When the bike is hot, the metal expands and the valves are all standing slightly open. Starting fluid overcomes the fuel being blasted through the valves, it explodes and starts. Keep on doing it that way, and serious engine damage can result.
Also, correct the air leaks around the intake boots, airbox boots, etc. to correct the lean condition.

[tom203]

looks like newer valve cover gaskets and new style allen bolts on intake boots. after reading about valve adjustment on bikecliffs site, not sure i want to fly into that project. Im still not sure what else to check? I did spray ether around intake boots. no increase in rpm. still stumped that it will bumpstart and run perfect once started

Well, you might be flying into more fun projects if you ignore the valves now. With any luck, previous owner might have not run it very long with this aberation- checking/adjusting valve clearances will make lots of tuning easier. New valve cover gasket is no assurance that valves were checked- might have just been leaking. Bump starting gives higher revs and lets things get going, but you could easily be weenie roasting your valves.The bike is 30 years old- give it a chance.


Add; Did you did see cmn1771 posts in 4cyl/drivetrain/clutch forum?

[Nessism]

The bike is 30 years old- give it a chance.

Good quote here...

[BassCliff]

looks like newer valve cover gaskets and new style allen bolts on intake boots. after reading about valve adjustment on bikecliffs site, not sure i want to fly into that project. Im still not sure what else to check? I did spray ether around intake boots. no increase in rpm. still stumped that it will bumpstart and run perfect once started

Hi,

You have to check it all. As stated above...

Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Rebuild Series, and the Stator Papers. All of these issues must be addressed in order to have a safe and reliable machine.

We're not trying to be mean or coy. We just want you to take care of your bike properly. Troubleshooting most issues is extremely difficult until all of the required maintenance is known to be completed and within spec. Keep us informed.


Thank you for your indulgence,

BassCliff

[Steve]

when bike is hot in the non start mode i put charger on boost. wouldnt that rule out weak battery?

Well, it might rule out a weak battery, but the "boost mode" might also kill other (expensive) parts of the bike.

.

[robz27]

you talked me into it

more heads are better then, mine?
im going to attempt checking vavles. with all the help you guys gave me so far, so fast, im confident your pointing me in the right direction. I have no prob tearing apart. not sure about physically measuring clearance. hopefully with this topic active and me re-reading bikecliffs vavle adjustment how to. I can check my valves
other then possibly ordering shims. I need gaskets and that suzuki valve tool? am I forgetting anything?