GS450T - High idle

[Anonymous]

One last question about an '81 GS450T.

All of a sudden the bike started idling very high 3000-5000 RPM, but only if the bike is completely warmed up; 15 minutes on the highway.

The #2 cylinder is burning very rich, but the #1 is fine.

Valves were checked and are adjusted correctly.

Seals around the air screws replaced.

Choke is manual (no cable) and off.

Tested the seals between carbs and head by spraying water on them and no change in RPM, so I think they are okay, but will probably replace anyway.

It sure is behaving like the #2 carb has the choke on. Is it possible for one carb to be choked, while the other is not?

I'll be removing the carbs and taking them in. Is there anything in particular that I should have the mechanic look at that might explain this problem?

Thanks.

 

[KEITH KRAUSE]

You say it happened suddenly. Because the rpm's rise so high only when it's warmed up, I suspect the o-rings in the manifolds or the manifold(s) themselves.
The water test doesn't always expose the leak.
First be sure the clamps are tight around the manifolds. Then also check the screws or caps(?) that are removed when you install a carb vacuum gauge to synch the carbs. If one of these came loose, you would have an intake leak. I don't know exactly where they are on your model.
If these things are OK, then inspect the manifolds and o-rings. Apply a coat of hi-temp' bearing grease to new o-rings. Torque to about 6 ft/lb.
A carb synch is always a good idea too.

 

[Anonymous]

Thanks for the info.

I think we'll just get new manifolds and O-rings before messing around with the carbs too much.

 

[jhw84]

please update!

please update!

Espumoso,
I too have a 100% stock '81 450T with a similar problem.

Bought it last July from the paper, fixed it up, and rode it. A month or so later, I noticed when i let it run leaned over on the sidestand, it would dump fuel out of the #2 overflow. Opened it up and sure enough, that float had taken on fuel. So $50 later (1 float and 2 float bowl gasgets) she was back on the road... However, after heating up, the idle would slowly climb from 1200, up, up, and up, to 4000! I rode it like that for a bit; when kept cold, it was ok, then we got alot of rain, so i parked it for a while, planning to get this gremlin out. Before I could, I took it out after Christmas for my future brother-in-law who was in for the holidays. Despite the fact that it was 40 degrees Farenheit outside, It was barely warm when the idle rose up again. Thouroughly aggrevated, I parked it on the porch and removed some parts, preparing to pull the carbs, beautiful weather or not! But, I had to go out of town, which lead to my discovery of this forum. Funny how things work, eh? (just not carbs... they are very much not funny...)

After searching this forum and learning so much (thanks guys!), i was planning to check my float levels and manifolds when i got back in town (presently at my girlfriends parents house), but after searching again and reading your post, i had to ask, did you get it fixed?!?

If so, what was wrong and how did you fix it? After reading this site alot, I think I may not have the correct float level (you mean they dont come preset? no rookie jokes, please!)

Ill let you know my results on Thursday, after i tear that b*tch apart!!

 

[jhw84]

My results

My results

Alright... After pulling the carbs and finding a suitable measuring device, i found that the float I had replaced was 3 mm too high. The other one was about 1.75 mm too high. After careful adjustment, she runs like new again.

Now, if only it would warm up a bit...

 

[Anonymous]

Glad I checked back because apparently I wasn't getting email notifications.

This thread morphed into the following thread.
http://www.thegsresources.com/_forum/viewtopic.php?t=29949&highlight=

My story is very similar to yours. One float had taken on gas and there was a crack in the manifold O-ring. Both of these were fixed, but the problem persisted. In the thread above, I figured out that the butterfly was hanging up on the throttle body, thus causing the high idle.

I just got a set of 450 carbs off an '83 and put them on, but now giving it gas causes it to bog down and stall. I'm just going to bite the bullet and do the entire carb cleanup series from the site here.

While I'm doing the cleaning, I'm going to put the plastic floats from the '83 carbs in the '81, set them correctly and see what happens. I don't have much hope given the butterfly problem, but if it works, my girlfriend will be happy to have her commuter bike running again. Mine is an 81 GS650G, with its own set of carb gremlins!

Bad weather (rain and more rain) and no garage have really slowed the whole process down!

 

[bgmart450]

I doubt this will help, but I'll toss it out there for kicks and grins.....

When I had removed the carbs off the 450S I didn't snap the throttle cable fully into the connection at the carbs. I got the cylinder at the end of the cable in fine, but neglected to pull taut the cable afterwards (there is this guide that the cable needs to snap into on the same piece as where the cyl fits in). I wasted a bunch of hours trying to find out why it was idling so high.

Again, it was a stupid error and I am pretty sure most have checked that, but in case you didn't you can learn from my dumb mistake.

 

[Anonymous]

I have indeed made the same error, but now I make sure there is a little slack in the cable