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**earlfor** · 03-23-2006, 01:11 AM

On my 79 750E (same as yours for tuning purposes) The fuel pilot screws were set to 1 1/4 turn out. The pilot airscrews were 2 turns out.

You have spark on cyl 1 but no power/combustion on that cylinder. Starting fluid does not combust either. I would check valve clearnace. I suspect the valves are not closing correctly and clearances are too tight.

How low is low compression? If compression is really low, I would expect the engine to "run out of steam" at a very low rpm.

Earl

Originally posted by The Kelzer

Aloha,

I just picked up a 78 GS550 that appeared to need major work.....but it was COMPLETELY stock so I thought I'd have a go!

I got the motor running on 3cyl in just a few hours....#1 is NOT wanting to cooperate. I've done a leakdown test as well as a compression test. All cyl's were about the same....low but acceptable considering it has 45K miles on it. I've checked valve clearance...all within spec.

#1 wont even fire on starting fluid. Yes it's getting a spark. (even switched #1 wire w/ #4 wire and #4 cyl ran cherry...#1 was dead)

I've pulled the motor and am ready to dive in but I have a few questions regarding the carbs.

The air mixture screw setting: What is it? The manual I have simply states "Do not touch the painted mixture screw on the bottom next to the float bowl of #3 cyl....it is set by the factory and any adjustment will cause poor running. Well during the carb rebuild (the carbs were HORRENDOUS !! The worst I've EVER seen, and I've seen some nasty carbs....I swear they were hairy inside!!) I unscrewed it. What is the setting supposed to be?

I got the motor to idle (albeit on 3cyls) and it would run nice up to about 4K (albeit on 3 cyls), then it falls on it's face and wont accept any more throttle. She revs to redline with no load.Any ideas why she wont accept a load?

So while we are at it........

Who wants to guess why #1 wont fire?

Aloha and mahalo,
The Kelzer.

**ddaum** · 03-23-2006, 09:57 AM

Here are the carb settings that I used during my rebuild, worked good.

GS550 (77-79) the specs are for the VM's

idle r/min 1100-1200
carb mik vm22ss
id no 47110
bore size 22 (0.87)
float height 24.+/-1.0 (0.95 +/-0.04)
fuel level 4.0+/-1.0 (0.16 +/-0.04)
air screw 2.0 turns back
cut away 1.5
jet needle 5dl35-3 (the -3 3rd notch??)
pilot screw 1.0
pilot jet #15
pilot outlet 0.6
needle jet 0-6
by pass 1.0
main jet #80

GS550 (80-82) the specs are for the CV's

idle r/min 1100-+/-100r/min
carb mik bs32ss (4 seprate carbs)
id no 47160 (us) 47170 (can)
bore size 32 (1.26)
float height 22.4.+/-1.0 (0.88 +/-0.04)
fuel level 5.0+/-0.5 (0.20 +/-0.04)
main jet #92.5
main air jet 1.6
jet needle (4bel2 us model) (5f42-3rd notch canadian adjusable needle)
needle jet x-6
pilot jet #40
throttle valve #135
by pass (0.9, 0.7, 0.7 us model) (1.0,0.8,0.8 canadian)
pilot outlet 0.7
valve seat 2.0
starter jet #35
pilot screw 3.5 turns back (mixture screw)
pilot air jet (us model #150) (#120 canadian)

These were originally posted by "first timer" HERE.

**The Kelzer** · 03-23-2006, 01:41 PM

Thanks guys for the specs, I really appreciate it!!!

Like I said, the valve clearance is within spec. The Compression is in the low 90 range and the leakdown is is less than 12%. Not great numbers, but w/45K on the clock....they are understandable. Also, All the cyl's are very close to one another so for #1 not to be hitting at all is very unusual.

I'm going to crack her open tonite and snoop around.

Any other ideas?

Aloha,
Kelzer

**vinny8524** · 03-23-2006, 01:53 PM

i had the same exact issues of 1 cyl missing ( would not even cold start w/starting fluid) , but eventually would fire off once it got hot. I chased everything down, valves, ign, compression, plugs, etc. went thru the carbs 2-3 times. It ended up being the little choke pick up tube bore was clogged solid in the bowl and the little hole for its pick up in the bottom of the bowl was clogged solid and she could not pull thru the choke system when cold starting. as soon as i cought my mistake and cleaned it, she has never started better. Just something to double check and think about.

Good luck
Vinny

**The Kelzer** · 03-23-2006, 08:08 PM

Mahalo Vinny,

I cant even get the beast to fire with the carbs off !!!

I'm going to attach a pic (if i figure it out) of the carbs.....they were unreal!

Aloha,
Kelzer

**The Kelzer** · 03-24-2006, 08:23 AM

Gross huh ??

Kelzer

**rckrzy1** · 03-24-2006, 12:23 PM

You have to be VERY carefull with those idle needles, when they say 1 1/4 from bottom, I mean a VERY VERY soft babies behind touch, OR you will break the tips off in the pilot jet and guess what , NO running till 1/2 throttle or higher. This can be tested by holdiong your finger over the air / pilot jet on the front of the carb. If you block this air hole the fuel will be sucked out of the main jet.

My 750 came to me with #1 and #2 not running due to the needles broken off in hole. Took alot of work to get the pieces out. BTW the other end is in the carb just the intake side of the butterfly, a small hole where the bypased fuel (for idle) get's to the engine.

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