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two things: cold #3&4 pipe and bogs in gear

  • Thread starter Thread starter Lulu7404
  • Start date Start date
L

Lulu7404

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I did a search yesterday and probably read 30+ pages. I do remember reading about each individual problem but tried to find the threads again and came up empty.
This is a basket case 82 GS750E being brought back to life.
I have done full carb cleaning with Berrymans and Robert Barrs orings
I have bench synched the carbs, twice now to make sure
New plugs, new caps were ordered yesterday, but I do get spark on each cylinder as is.
It has stock jets and a supertrapp 4-1
I have the mixture screws all set to 2.5 turns out as a base.
I think I am lean based on having 4-1 pipes but I cannot do plug chops as it bogs badly when I put it in gear. Neutral revs just ok. I can get revs to upper range but not smoothly. It's not crisp off idle, I have to slowly open throttle.
1. pipes on 3 and 4 are cold enough to touch after limping around the block in first and second gears
3 and 4 would eliminate coil correct? not 1 and 4 or 2 and 3
when I try the highest idle the screw on cylinder 4 makes no difference, I even closed it with no change.
When checking for spark, I can pull #4 and watch spark against cylinder head and bike runs, if I pull plug on first cylinder to check for spark bike won't run.

Sorry for so much info, but wanted to include everything I have thought about.

any ideas of what to check next while I wait on new plug caps to arrive?

edit: stock airbox installed, and I did attempt a vacuum sych but it appeared to be pretty synched... I will be doing that again. I have also adjust the valves to the best of my ability. Sounds like a sewing machine. actually kind of loud but doesn't even have a mile on it since. It was not running when I bought it.
Thx in advance
 
Last edited:
I'm guessing your plug wires are not on the correct cylinders

It's 2-3 and 1-4 for the coils

You're bogging because you're running on 2 cylinders
 
Is there fuel in the float bowls for 3 and 4? Pull those plugs after running it and getting cold pipes. If they are wet, it's a spark problem. If dry, it's a fuel problem.

HTH
 
ok, I just went out to garage to look (because I did remove coils to do some early cleaning.
My coil wires are labeled 1 though 4 but is it possible to put coils on wrong sides?
My left coil is labeled and attached to cylinders 1 and 4
my right coil is labeled and attached to cylinders 2 and 3
If you wrote it in your post from L to R I have my coils on wrong sides which would effect timing? and not fire all cylinders???
Thx Big T for your input I will check the clymer manual I have and see if I have them on backwards.
 
mister cinders. fuel flowed from drain plug on 4 so i didn't check 3. thanks. i hope big t was on to something with coils on wrong (if that is possible mounting wise)
 
well if cylinders 1 and 2 are firing, and cylinder 4 is going to the same coil as #1 and #3 is going to the same coil as #2 then I'd say you're OK there.

Have you run a compression test on the motor?

Are the plugs for #3/4 wet with fuel after running? Should be some on there if they're getting it but not burning it.

Is the spark from #4 fat and blue? Might want to check your plug caps for resistance. Stock are about 10k, NGK's are about 5k. When the stockers fail they tend to go very high resistance - they may still spark but it would be weak.
 
Mike, the coils are working, but if on wrong cylinders, the timing would be off I think so hopefully tonight I can check that and run it for a bit and pull the plugs on 3 and 4 and check them for fuel. Tried getting a compression tester from autoparts store but it didn't fit the cylinder holes. So i just did the thumb over hole test. Has compression, just not sure how much. Spark was weak, new caps ordered yesterday waiting on them to arrive.
I can feel heat in pipes, but 1 and 2 are too hot to touch almost instantly.

thx

off to work, but hope to have more things to check tonight.
thanks again everyone on the GSR!
 
Brad

Your coils and plug wires are correctly mounted

You have a carb issue - as the other posts ask- are the plugs wet on #3 and #4?
 
It does sound like a fuel issue, but it might also be more. With the coils grouped as 1-4 and 2-3, you can eliminate a problem with the coils if cylinders 3 and 4 are not firing. As mentioned before, a coil problem wouldn't be with those two cylinders only. With individual carbs, you can eliminate a carb problem to expain two dead cylinders. So with cylinders 3 and 4 not sharing much of anything, you need to diagnose those two cylinders seperately.

Check for fuel in both carbs, spark at both plugs, resistance of both wires, etc. You may find a clogged pilot jet or air screw on 4, and a bad plug wire on 3, or something like that. You might try pulling the plugs from 1 and 2 to see how what happens, you may get a clearer picture of what happening (or not) without the two 'good' cylinders running. You might also compare the spark from 1 and 2 to 3 and 4, and compare the resistance of the wires as well.
 
Sounds to me like #3/4 main jets are clogged with debris. Does the engine idle good ? This new E10 fuel wreaks havoc if left sitting untreated in your carb bowls !!
 
update

update

ok, rode around block again tonight. same bog from idle, but i ran it out some down street and at about 5k it surged and pulled quite hard for what we seem to think is a two cylinder currently or did a different jet system take over at a wider throttle position and the other cylinders kick on? is that a wild guess?
it died when i pulled back into driveway and i pulled all the plugs in order 4>1 and grounded them against head. all had spark, not sure if weak as all have original plug caps still.
when i pulled either #1 or #2 the bike would not start it would run with both 3 and 4 out...Here are the plugs in order starting with #1
plugfrom1.jpg

too hot to hold
plugfrom2.jpg

again hot
plubfrom3.jpg

number three not hot at all
plugfor4.jpg

and #4 again not hot at all
If there was fuel on plug, it wasn't much so I am not sure it is getting to plug. Would that indicate not enough compression in cylinder to pull in mixture if jets turn out clean?
pulled carbs again. drained gas from all four bowls and will check jets later tonight or tomorrow. need to borrow multimeter from same buddy that has carb vacuum synch to check wires from coils.
Thx again for all the ideas, if anything else seems possible please post up
 
Lulu7404 said:
ok, rode around block again tonight. same bog from idle, but i ran it out some down street and at about 5k it surged and pulled quite hard for what we seem to think is a two cylinder currently or did a different jet system take over at a wider throttle position and the other cylinders kick on? is that a wild guess?
Click to expand...

Bingo. Mains kicking in. Take them carbs back off. Check the pilots. Also check the idle screws and make sure you don't have tips broken off and plugging the holes. Awww heck I'd just re-dip 'em for 24 hours again. If you're careful you ought to be able to re-use your o-rings since you just rebuilt 'em.
 
thanks to everyone

thanks to everyone

I would thank you all individually, but almost all of you suggested jets, so thank you everyone. Here is how it started:
4bowl.jpg

black crud inside the float bowl, then:
4plug.jpg

more crud on plug.
This is #4, three was the same, both pilots were plugged. Yes I checked all four while I was in there.
Will check mixture screws as well tonight after work, this was all the time I had at lunch.

Thx again, maybe I will get to hear a 4 cylinder for the first time tonight!
 
That was it! Thank You!
I am curious as to where that black crud came from. I wonder if the gas T at the carb is deteriorating? Anyway, mixture screws were not broken off. Man what a difference in sound and feel. Another trip around the block turned into 4. I have no lights and my gas tank is a overflow tank from autoparts store so i didn't stray far from home. It still needs to be vacuum synched and mixture screws tuned to highest idle, but wow what a difference two cylinders make... haha. Now to finish the brakes.
 
I may do that again before she is put on the road. I have already dipped them twice, as is. Figuring out where that black crud came from needs to happen first or it may happen every time I run fuel through them. This was the first time this bike has run close to normal. Plugs over mixture screws are new, all o-rings new from R Barr. I know I tore at least one float bowl gasket, so new but not sure I bought 4 new ones. As mentioned, I wonder if the T for the gas inlet is breaking down...
But what was that lighter colored material? Was that dried E10?
Neither #1 or #2 were like that, I am assuming because they have been working and the fuel has not been sitting in carb as long.
 
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