Speed Problem

1518 Views 13 Replies 6 Participants Last post by Nathan, Feb 26, 2011

Nathan

Discussion Starter · Feb 14, 2011

My '82 GL500 has this weird problem, it wont go over 55 mph in 5th gear without using the choke. It will go well over 55 in 4th gear without the choke though, and runs fine in 5th gear with the choke out. Its just really annoying to have to work the choke while riding in heavy traffic with alot of red lights and stuff.

So far all I have tried is adjusting the fuel/air mixture screws and that didn't effect it.

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ramprat06

· #2 · Feb 14, 2011

This certainly points to a carb set up in my opinion. A good cleaning is in order. Can you give us some more history on the bike? Mileage etc. It doesn't sound electrical to me from the description.

Thanks for filling out your profile information, that really makes things so much easier for us. You will get a lot of help here.

Welcome to the best CX/GL place on the planet.

Joel in the Couve

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Nathan

Discussion Starter · #3 · Feb 14, 2011

Its got 22k miles and been garaged kept for most of its life. My Grandpa bought it in like '92 and drove it to work every day for about 5 years. After that it sat in the garage until 08 when he finally gave it to me and I got it to its current state with just a repair manual. I've taken the carbs apart and soaked them 5 or 6 times probably in the last couple years. This is the last problem to fix before I would call it finished.

According to this picture that I found on another post here, my best guess is that there is something inside the passageways for the fuel/air mixture screws. I think they are the problem because adjusting them all the way in to taking them completely out doesn't really change much. I just don't know how to clean in there with those sharp bends and stuff, any ideas?

But I'm thinking its not a carb problem since it will go faster in 4th gear and will rev to red line in neutral.

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CXPHREAK

· #4 · Feb 14, 2011

It might also be handy to know how many miles you have put on it since you put it back on the road after it's lay up.

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Nathan

Discussion Starter · #5 · Feb 14, 2011

About 3k.

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Nathan

Discussion Starter · #6 · Feb 14, 2011

I also ran a good deal of Seafoam through it during those 3k miles.

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Blue Fox

· #7 · Feb 14, 2011

Welcome to the forum, Nathan. When you had your carbs apart, did you maybe swap the jets into the wrong towers? They will fit either way, but the larger number goes into the brass hex fitting. Reversing these, even on just one carb, will cause problems similar to what you are experiencing.

Thanks for filling out your profile too.

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ramprat06

· #8 · Feb 14, 2011

The best way to really clean everything out completely is by using an Ultrasonic cleaner with Simple Green. Harbor Freight has a good one many here have used, I think they are on sale now for $69 or so. You also need to get a very tiny drill bit for that low speed idle jet. That picture you posted is one from Larry ( LRCXed, our resident carb guru and moderator). He has written a book on this, but a lot of this information is posted in the Quick Reference section of the General Discussion topics.

It's hard to say why you are able to rev all the way in 4th yet not in 5th, but it may just be the carb has already bypassed the lower flows, and it struggles to get wide open in 5th. In any event, a more thorough cleaning ala Larry's way will surely afford you the peace of mind there, and then if the issue still persists, other avenues can be looked at.

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Nathan

Discussion Starter · #9 · Feb 14, 2011

This one?

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ramprat06

· #10 · Feb 15, 2011

Nathan said:
This one?

Yep, that's the one.

And Nathan, a snippet from the post that is in the Quick Reference is worthy of copying here. Written by Larry......

As you know they can be a bit of a pain to get running right. The main issue they have is in the low to mid range RPMs. They have hesitations and flat spots as well as hard starting issues after years of neglect and sitting around with no use. What I have discovered is that the low jet that's pressed into the early style carbs, as well as the screw in style of the later model bikes, has been the culprit causing the issues we have been experiencing. The low jet has a very small hole in it (.018) and 8 holes for emulsifying the fuel. The .018 hole in the center of the jet has to be cleaned out manually with a drill bit to get it cleaned out properly after it is pulled out.

There is NO cleaner available including the Ultrasonic cleaner that will remove the deposits that build up in them. This alone makes a world of difference in how they run, but will not totally fix all the issues if the circuit chambers are not cleaned out as well. The book outlines a process to clean them manually, but strongly suggests using an Ultrasonic cleaner to do the job properly. Believe me when I tell you that these bikes can and will run like new when the carbs are cleaned and rebuilt properly. I have done a few hundred of them all with great success.

Let me add that I sent my carbs to him last spring for an overhaul and a week later they came back factory new looking and running, already balanced, and tested on the road. Well worth the $250 or so.

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Nathan

Discussion Starter · #11 · Feb 25, 2011

After much cleaning, everything looks fine to me. But I did discover that the lines coming from the petcock were wrong. The breather tube was connected to the vacuum port on the carb, and the vacuum line from the petcock was just hanging back by the airbox. Haven't had time to test drive it yet, but do you think this could cause my problems?

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thackney

· #12 · Feb 26, 2011

yes.

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Reg in Bristol

· #13 · Feb 26, 2011

Sound very much like a restricted supply

If properly connecting the tap doesnt sort it

( you may want to check the tank strainer too if fitted )

there's a work around to mod the often troublesome vac tap to a simple on off affair

havent had to do it myself as I have always used the basic taps but I expect the info's here somewhere

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Nathan

Discussion Starter · #14 · Feb 26, 2011

Reg in Bristol said:
Sound very much like a restricted supply

If properly connecting the tap doesnt sort it

( you may want to check the tank strainer too if fitted )

there's a work around to mod the often troublesome vac tap to a simple on off affair

havent had to do it myself as I have always used the basic taps but I expect the info's here somewhere

Yeah I had found the post that explains how to make it act like a regular carb instead of a vacuum carb, which is what made me go look at it.

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