Spark and fuel to carb but not to cylinder

[Guest]

Hello all


I've been working on my 85 GS400E all winter here in Guelph Ontario

So far this winter i have
-Dipped carbs in pine sol for 2 days
-Barr Or ring kit, cleaned out all holes
-Replaced all electrical connections on harness
-coil relay mod
-horn relay mod
-headlight relay mod
-new (legit) sh220 r/r
-new stator
-new spark plugs and plug caps
-valve clearance
-new clutch springs
-inline fuel filter

Timing is automatic

Last year I had an electrical issue and with all the work done now I'm getting a big fat spark.

Carbs are full of clean gas, float bowls are also full.

Will turn over forever without a hint of trying to fire up except the occasional backfire. It started backfiring slightly more after valve clearance. Even with WOT and full choke I pull the plugs and they are bone dry, don't even smell like gas. Quick start doesnt help a lick

I pulled the carbs and there was either gas or quick start all on the surface of the intake ports.

I was hopeful it would be a valve clearance issue, but since it didn't help I'm thinking now my valves may be leaking. 33k on the bike and I've never had a look at the cylinders or valves, from purchase condition the POs probably never did either.

Ordered a compression tester to try next, although if I put my finger on the plug hole I can feel compression and suction and suction on my hand if I cover the intake boot.

Im thinking there is a leaky valves that are pushing my air/fuel back at the carbs. When i take the head apart I will lap or replace the valves and get the cylinders honed and new gaskets, anything else I should look at or do/replace while I'm in there?

Also I will look at carbs again could a stuck needle explain these symptoms? I adjusted my jet needle to the lowest clip position to try and get it to run leaner in the midrange.

Thank you

Safe riding

Uladimir

[Tom R]

Plug wires reversed?

[Uladimir]

Plug wires reversed?

Plug wire are same as usual so they should be good

[Steve]

So far this winter i have
-Dipped carbs in pine sol for 2 days

I am sure your carbs look all sparkly clean on the outside and smell fantastic, but I am not yet convinced that Pine-Sol is the proper chemical to use for cleaning out all the passages on the INSIDE of the carb, where all the problem areas are.

-coil relay mod
-horn relay mod
-headlight relay mod

You have added relays to the three fused circuits on the bike. Did you bother to check the INPUT of those three circuits before adding all the relays? There is a pretty good chance that ONE relay that feeds the fusebox would have done the same job.

-inline fuel filter

What was your souce for the filter? If you just went down to the corner auto parts store, there is a good chance that filter is too restrictive and will not allow proper flow. There are already three filters in your fuel system, one on the petcock and one at the inlet of each carb, so there is no good reason to add another. However, if you feel you really DO need the added restriction, at least get a filter from the lawn tractor store and make sure it is one that is designed for a gravity-flow fuel system, not one with a pump.

Will turn over forever without a hint of trying to fire up except the occasional backfire. It started backfiring slightly more after valve clearance. Even with WOT and full choke I pull the plugs and they are bone dry, don't even smell like gas. Quick start doesnt help a lick

Right here are your two biggest problems. First of all, THROW THE QUICK START IN THE TRASH. There is no need for it around a GS. Next, the "choke" is not a choke system like you find on a car that actually blocks off (chokes) the inlet of the carb. It is an "enrichener system" that uses separate air and fuel passages to provide a richer mixture for starting the bike. It relies on the high vacuum of a CLOSED throttle, so even cracking the throttle open a little bit will defeat the system. You need to revise your starting technique.

I have not seen an '85 400, but I am going to guess that it has the "choke" lever on the left handlebar? That was typical of all GSes, starting in '82.

To start the bike cold:
1. Apply full "choke"
2. Ensure 'kill' switch is in the RUN position
3. Turn key ON, verify that green NEUTRAL light is ON
4. Pull clutch lever (unless you have disabled this "safety" feature)
5. Push starter button
6. When engine starts, modulate the speed by moving the "choke" control, NOT the throttle
7. After about 30 seconds, the engine should be running comforably, check throttle response by blipping the throttle. When you get decent response, the bike is ready to go.

Did you notice that NOWHERE in the starting technique was throttle useage mentioned until AFTER it was running? ANY application of throttle will bypass the enrichener circuit, and you will be trying to start your engine on the leaner "normal" jetting.

.

[mrbill5491]

Plug wire are same as usual so they should be good

No, he means did you get the plug wires back in their proper firing order on the plugs.

[wymple]

If you have the hot spark you claim to, SOMETHING would have to happen when you prime it. I prime not with ether, but with carb cleaner or gasoline. You effectively bypass (for a few seconds) almost any function of the carbs themselves when you prime it. If it doesn't make a good effort or even fire up for a little bit, you do not have the electrics you think you do. If something is mechanically out of whack it would at least backfire....plenty. I have never seen an engine with fuel on the air filter that wouldn't go if the juice is there, unless flooded (which you don't have). Start with a timing light to see if the spark is there and when it's supposed to be.

[Uladimir]

Oh okay yes the plug wires are in the same order it's only 2 cyindersso straight forward enough.

Steve thanks for all the pointers, Berrymans in not allowed unfortunately in Canada but I did spray all the passages on the inside with carb spray and checked them visually. If carbs continue to give me grief I'll work on sourcing something stronger.

I didn't even think about using one relay, I had two in there before but re-did the wiring in 10 guage and added the one for the horn.

Filter came from z enterprises but I will take it off for now at least. I tried to put it on before and ended up ditching it because of a leak but thought I could put it in this time. I think I'll be better off without it.

I'll try the correct starting procedure tonight and see how it goes. I bench synced the carbs, but I'm not sure how far in the idle adjuster screw should be, from memory there's just a hairline visible at the bottom when it's set for 1000rpm ish idle.
I had it cranked in so maybe it affected the choke circuit as you described.

[Uladimir]

So turns out everyone was right

The spark plug wires were routed fine but of course the grounds that are the important ones going back to the igniter were reversed. So Wymple was correct it was an electrical issue. While I was at it I tightened the intake book bolts as well as the ones on the exhaust. I checked the carbs over and jets looked clean. I took the fuel filter out of the line, primed the cylinders with carb cleaner and she fired right up.

I did do a compression test too. Tested each cylinder 3 times, the one was 150 on average and the other was 175. Within spec but my Clymer says they shouldn't be more than 13psi difference.

How do I go about correcting this? Will I need a valve job? Or maybe I should look at my valve clearance again as they were pretty tight and maybe the carbon broke down after I adjusted them and loosened one up?

[Steve]

I did do a compression test too. Tested each cylinder 3 times, the one was 150 on average and the other was 175. Within spec but my Clymer says they shouldn't be more than 13psi difference.

How do I go about correcting this? Will I need a valve job? Or maybe I should look at my valve clearance again as they were pretty tight and maybe the carbon broke down after I adjusted them and loosened one up?

How much has the bike been run recently? How about in the past few months? How about in the past few YEARS?

If it has not been run very much, take it out, give it a good "Italian tune-up", run it for several hundred miles, then do your compression test again.

By the way, did you do the test correctly? Warm engine? Both plugs out? Throttle held wide open?

Oh, if your clearances were tight, that did not help anything at all. And if there was carbon that "broke down", it would make clearances even tighter.

.

[Uladimir]

Clearances were tight before I adjusted them so I left them at ~ .08 - .01 mm, so a little tightening should be ok.

The bike only did maybe 1500 miles last fall and that's about it since the 2015 riding season, I've just got to line up this ridiculously priced Ontario insurance and I'll gladly do the "Italian tune-up" and report back. Engine wasn't warm as I did it before noticing my wiring issue so I'll try again.

Thanks for the help

[Steve]

Clearances were tight before I adjusted them so I left them at ~ .08 - .01 mm, ...

If you left them at .01 mm, they were even tighter. Hopefully you moved the decimal and really meant .10 mm?

.