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'77 GS750 running only on 3 cylinders

  • Thread starter Thread starter Beaver
  • Start date Start date
B

Beaver

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I podded my bike about a couple of months ago. It didn't run perfectly, but it was better than before I started. I realised that there was more work to be done but that could wait. I have now lost my #4 cylinder. I have searched a little on it and just want to check to see if my conclusions are correct for troublefinding the source.

I check the plugs for spark (clean them if nescessary)
Test the compression
Clean the carbs

For the record, the header doesn't warm up with time or higher revs, it just stays dead cold. When I podded the bike I changed the main jet and cleaned everything in it that I could. Europe isn't blessed with all the wonderfully toxic chemicals that Americans can happily buy off the shelf so my carb got nowhere near the cleaning I would have liked to have given it.

Any other pointers anyone has would be most appreciated.

Cheers

Angus
 
Ive had cyl.do the same thing and except for bad coil once,its always been carb problem ,one time after cleaning two cyl had quit went thru them again and everything worked out fine good luck
 
Last edited:
As you've just lost No.4 there would appear to be no underlying ignition problem (or else No. 1 would be out as well). As you suggest, check for a spark / clean the plug / check the lead for cracks etc.

If you've got a spark you can do a very quick compression test - just pop your thumb over the plug hole (your bike will still fire if you've got really low compression).

As that cylinder doesn't run on any throttle opening I'm guessing it's not blocked jets (as they would all have to be blocked). Maybe your float has got stuck and there's no fuel in the bowl. Try pulling the floatbowl drain plug to see (you could just try tapping the bowl before even doing this).
 
Sweet, thanks for that, will get back to you with results.

Cheers

Angus
 
Europe isn't blessed with all the wonderfully toxic chemicals that Americans can happily buy off the shelf so my carb got nowhere near the cleaning I would have liked to have given it.
Click to expand...

Do you have hot water and detergent? Strip your carb bodies and boil them for a couple of hours in a pot. They will come out nice and clean.
 
Beaver said:
I podded my bike about a couple of months ago. It didn't run perfectly, but it was better than before I started. I realised that there was more work to be done but that could wait.
Click to expand...

Did you rejet the carbs? Sounds like it was tuned quite well for header (4-1?) but with the addition of the pods...you slipped over the edge of too lean. :-s

A good carb strip and soak is where I'de start. Check the jetting and let us know "what's in there" and it'll be back up and running right. ;)
 
beav,
uv got at least 2 problems. Assuming all was good b4 you went with pods (K&N's , whatever), better intake breathing (K&N, good pods) without an other changes will assuradely make things go lean. Rejet, rejet, rejet.

It will run like crap unless you do.

Ok, other problem is #4 out. 1)pull plug, look at it. Look clean? Oily? Carbon coated? - all important for diagnosis. I

Test ignition for #4. You sure it is spark and NOT a fuel prob?
Is there a Fat Blue spark when u turn starter with plug removed and plug held/grounded against engine block? If Yes then good. No then problem is w spark.
 
Thanks guys for all your help!

I had already pulled my carbs off in my haste to clean them when I remembered that I should start with spark first. Problem found in under 3 minutes, one of the plugs wasn't firing properly, and now that it is replaced I am up and running on all four again.

Thanks to everyone for their input :D

Angus
 
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