[John Palmer]

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Hi All need a bit off advice on my gl1500 1989 120,000 on clock just developed a flat spot on acceleration in o/d at around 2000rpm if i drop down a gear no problem. otherwise bike runs like a dream. PS just out of curiousity was wondering what kind of life span the 1500 engine and gearbox has?

Its not to serious but it seems to take a while to pick up no misfire think may be carbs? any advice would be appreciated
Regards JOHN PALMER

 

[Renegade]

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John.. Take a look back in the postings and you will find a lot of info. on the GL1500's for performance quirks.. The engines are very strong and should last for a long time.. However, if memory serves me, the carbs are another story.. One of the postings mentioned that the metal they are cast from is pourous and once the outer plating wears away, the cast metal begins to disintegrate. This is especially true around the throttle shaft bores. Once the shaft bores wear, it creates a lean mixture in cruise which is not evident at lower gear settings. Once you are infinalgear, the cruise circuit in the carburetor comes into action and the mixture is controlled by the diaphram and needle sitting in the fuelcontrol cylinder. If there is too much ouside air pulled in past the throttle plates, the vacuum pressure drops and the diaphram is not sucked (pardon the word) down low enough to produce a richer mixture.. Hence, the flat spot you are experiencing. There is sometimes a back-fire experienced in that split second where the mixture is too lean, itis delayed in firingand the intake valve has not completely closed yet.

May I suggest balancing the carbs first, and go over all the maintenance requirements needed at that mileage. Inspect the spark plugs for wear, air & fuel filters for blockage and the timing belts for stretching.. Delayed valve sequencing will cause the valves to close late.. Renegade

 

[FitzAl]

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On an 89 I think the carbs will be the problem, most owners never took advantage of the recall for the carb fix. A temporary fix I seen done is to lift the console and air filter cover and spray wd40 onto the black plastic sliders in teh carbs. If the flat spot goes away for a while then you know the carbs will need stripping and cleaning.

 

[corneo]

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John,
keep in mind to do baby steps first. Check, clean, spark plugs. Try the WD40 trick. Make sure the gas filter is clean. These are thingsthe shop will do before they go in to heavy work.

Most times problems are very simple. :waving:

 

[Heffo]

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corneo wrote:

John,
keep in mind to do baby steps first. Check, clean, spark plugs. Try the WD40 trick. Make sure the gas filter is clean. These are thingsthe shop will do before they go in to heavy work.

Most times problems are very simple. :waving:

Makes sense. Do the easy things first even if you suspect carbs trouble. At least you can eliminte the easy things in a short timeif the carbs really are the cause.

 

[John Palmer]

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Many thanks, my bike is due a service so will carry that out, will also spray carbs with WD 40.

Exhaust collecter box been welded that many times could that have any effect.

need to get it sorted as off to europe next year, AGAIN MANY THANKS WILL LET YOU KNOW WHAT FIXES IT

REGARDS JOHN & CHRIS

 

[JDuggan]

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John, I doubt if welding the collector box would have an adverse affect. Most of us have lumps of weld all over our collectors and it doesn't cause problems. Good luck in Europe next year.

 

[glennuk]

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john try running 2 tanks of fuel with redx in it and check air fillter as i run a 88

which also has over 100.000miles on itand the only problems i get from the carbs is

dirty fuelafter touring

 

[englishted]

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John, it sounds like the infamous flat spot all right. Do the spray trick and you will know soon enough.