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1988 gs450 won't Rev past 6k

  • Thread starter Thread starter chris032188
  • Start date Start date
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chris032188

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I am having trouble with darn bike..

While in neutral if I rev bike it'll go up to 8k then drop down to 6k and start to sputter.

I've cleaned carbs, replaced float needles, Che ked for vacuum leaks, check compression and nothing seems to do anything.

Bike does have HD peanut tank conversion but I tried putting original tank on and that still does the same thing.

Any tips to fix this will be greatly appreciated
 
Bike does have pod filters and straight pipes with 12 baffles in. Jet kit is from 6sigma
 
Checked clearance they appeared in spec. Just had bike Runnin so can't check them again. Gonna pull carbs and soak them again and I'll check clearance again tomorrow.
 
Carbs cleaned and reassembled out back and bike still having same issue. I have the line for the original pet cook suction plugged up since current rank doesn't have that.. This is correct thing to do correct?
 
Also checked the valves again all were in spec.. One intake was. 03 so it was close but still OK.

I don't think it would effect WOT but the new jets 6sigma sent me the pilots have holes throughout the side of jet. I'm uploading video now to show how it revs


I have noticed that going back to the stock size main jet of 120 as opposed to the 134 and 140 make the bike able to rev a little bit higher, but when I rev bike and cut motor and check bike the plug looks a little ashy..


the first one is rolling onto throttle second one is just going straight to FT.
 
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I am wondering if because I have a 1/4in line running from tank to the carb that im restricting the fuel too much? I beleive stock line on bike is a 5/16th? The HD petcock is a 1/4 in.. Maybe I just need to go bigger on that?
 
maybe the floats are wrong height? I remember on one of my twins..either the 400 or 450?? the CLYMER BOOK IS WRONG..
 
The floats are set to 22mm the manual i have says 21.4 to 23.4... Could the smaller 1/4 fuel line I have on be restricting the flow of fuel enough to make it not be able to hold a high RPM?
 
It sounds like it is running out of gas. Reving higher on smaller main seems to confirming your theory about too small of a gas line. Also sounds like it is running on one cylinder.
 
OK so there's two nipple on inside of carb that I never capped or anything. I just did now
NXUf0d2.jpg
are these supposed to be connected somehow or capped
 
With them capped the bike will Rev to redline but the float doesn't engage and gas comes out of the holes on the intake end of carb
 
There is a link to a service manual and a carb rebuild guide for the GS450 on BassCliff's web site http://members.dslextreme.com/users/bikecliff/

I looked in the carb rebuild guide but couldn't see the same nipples that you are referring to, but maybe you will see them since you know what you are looking for. Give either of those two links a try and see if you find a pic of the carbs that will show what you are looking for.
 
Thanks for help guys - I have the same manual from that website and cant find anything on it.. I think I may try using a 2 on them to vent them out to one hose and see if that helps
 
Try setting the float height to 26.6mm. There is a discrepancy in the info concerning the float height. I tried setting my 81 450S to 22.4mm (as per the manual) and the floats would interfere with the bowl. It's running great set at 26.6mm. :)
 
Had float height to 24 and it wouldn't start. Back down to 22 it starts. With the 2 holes linked it revs full rpm but float doesn't engaged with them connected at a tee and the tee open it won't Rev past 8k. I'm stumped
 
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