'79 GL1000 Update, surging!

[yawjansen]

Howdy all! A little update. Plus a surging at idle issue.

I've done the belts, replaced the points and set static timing, replaced coils, wires and caps and condensers, rebuilt carb rack (Randakk video and kit), dynamic sync the carbs, oil and radiator fluid change so far...It starts right up! Idles good too aside from a tendency to surge to around 3000RPM and kind of hang there then drop back down. It also sticks when I give it throttle then slowly comes down. (I've done some forum searches but wasn't finding anything specific.)

It can't be linkage as it surges at idle. Also, when it surges at idle or when I rev it and it sticks, all four cylinders do the same thing, no off man out. I noted this when I had the Carbtune sync too hooked up.

Thoughts?
Thanks
Pat

[robin1731]

Could be a vacuum leak. Could still be out of sync. Both of those will cause surging and "hunting" at idle. A sticky ignition advancer can cause issues too.

.

[Whiskerfish]

Yep. What he said. There are like 16 or 18 possible causes but I put vacuum leak and synch and throttle cable free play/ operation at the top of the list.

[yawjansen]

Hmmm, I'm thinking vacuum leak as well. The carbs are synced and it exhibits the surging and sticking with all throttle cables removed. I have replaced all of the vacuum tubes and clamps as well. Thinking it must be a gasket. Any thoughts as to where a leak that affects all four cylinders evenly may be? Could be that all four CV slides are catching?

[gltriker]

Carbtune synch it , again , with pilot fuel screws set at 3 turns out from seat.

[Whiskerfish]

Make sure it is up to full operating temp and then tighten the Intake clamps. When cold those clamps do not work well on the old rubber. When the rubber is good and hot it becomes pliable and the clamps will do their job better.

[Earl43P]

https://ngwclub.com/forum/viewtopic.php ... ws#p782417

Read post #5 for another vacuum leak source.

[yawjansen]

Quick update! And huge thanks to all for the advice so far!

I turned the pilot fuel screws out 3 turns and tightened the intake clamps several times over 15 minuets, nothing heroic but they are very tight now. I also adjusted the idle screw out a little and al of the above seemed to work! The bike no longer randomly surged and returned to idle after revving as expected!

Took it for a first gear spin around the driveway, first ride on it! and after several minuets the ideal seemed to get real low and it started stalling on me. I turned the idle screw in a few turns and the bike exhibited the "slow to return to idle after revving problem" again....though not as bad. Guessing re sync as stated above and continue hunting for vacuum leaks?

[gltriker]

Yes. Takes time to sort out the issues.
Everyone had to do this same process on their GL , too.

[yawjansen]

Thanks Cliff! Good to know. I gotta say, when I took it around the driveway in first, it felt GOOD!

[gltriker]

2cd gear through 5th is even better !

[yawjansen]

Hey ya all! Thanks again for the help and suggestions so far. Here's the update, no longer surging but still hanging a bit and slow to return to idle. Power's a bit low in first gear riding around the driveway as well. Please see video! (Sorry not sure how to make it so you don't have to down load...)

20200830_160238_1.mp4

(14.39 MiB) Downloaded 30 times

Fuel Screw is 3 turns out and all the carbs are synced, all rubber intake boots are real snug and linkage is all free. I'm thinking the timing may need another adjustment as cylinder 2 is running a little cool? I'm also wondering if my CV slides are hanging causing the slow return to idle. When rebuilding the carbs I used some Emory cloth on them and got them real smooth but wondering if they may be a touch "tacky" as well. One other thing that all seems connected, on start up, choke out, I have to screw the idle screw in a couple turns and as the bike warms I screw it back out to avoid high idle.

Any and all toughs appreciated!
Cheers
Pat

[Whiskerfish]

SNIP One other thing that all seems connected, on start up, choke out, I have to screw the idle screw in a couple turns and as the bike warms I screw it back out to avoid high idle.

That is a specific symptom and I am pretty sure it is still indicating a sizeable Vacuum leak somewhere. Are you using fresh ORings between the heads and the Intake runners? Make absolutely certain they are not pinched and are sitting up in the recess's before bolting things down. I use a bit of White grease to hold the ORings in place before bolting things down.

On the slides the critical area is the brass sleeve and the chrome tube. I use old worn out green scrubie inside to make sure it is super clean. It seems to make sense that a hanging slide would cause a hanging idle but I have never found that to be the case, and usually end up find another cause.

[yawjansen]

OK, Whiskerfish, I checked the o-rings and they looked good. Re-checked sync and also good, real good. I did a round of tightening of the intake manifold rubber and acorn nuts and it ran about as good. Still missing coming out of idle into first. and still hanging a bit.
I did a compression test and got 175psi on 1 and 3 and 155psi on 2 and 4. Since the plugs were out, I re-gaped them all. 2 and 4 were over .030 and that makes sense as the two cylinders were always slow to heat up (hand check to the exhaust manifold). This resulted in the bike firing right up! It still exhibited surging but I decided to take it into 2nd gear in the driveway and it got on it! Not too much missing or back firing. Still hung up in first and idle though.

Decided to pull carbs off bike again to double check CV slides etc...found what seen to be good movement. Carb 4 was exceptionally clean so that was a bit alarming...

Question, aside from intake manifolds boots and o-rings, where would the next biggest vacuum leak present itself?
Also, cylinder 4 is still operating pretty cool. Given the fairly spotless condition of number 4 carb I'm guessing it may be having a fuel starvation issue? Could a "dead" cylinder be causing the surging and associated issues.

Here's a spark plug picture from left to right 4-3-2-1

20200901_133455.jpg (74.18 KiB) Viewed 266 times

Thanks for checking it out!
Pat

[gltriker]

Start with a new set of spark plugs and a tank of fresh gasoline before going any further.
A clean OEM Honda air filter element is best practice, too.

What do you mean saying #4 carburetor is exceptionally clean?

How about the float bowl retaining screws and their complementing carburetor body threads? Stripped out and not adequately sealing the gasket?