Back for more help *eye roll*

[Gorminrider]

O gee what a drag...sooty plugs are usually considered to be overrich air-fuel -that said, it's really pretty common on old bikes diagnosed in a shop while idling a lot...a long run is what these "plug diagnosis" refer to and it's assumed the bike is running ok , so the fix is offered to use a hotter plug. But do check you are running good, correct plugs of course.... It might be you are missing sparks (sigh)
... running rough all the time is the bad one- DO check all the cylinders are firing. Often bad lowspeed is a missing cylinder-you can tell easily by starting the cold bike and checking the warmth of pipes.....needn't say don't burn yourself. If it's missing cylinders, that's a big clue. If it's missing a pair, that's a clue.

if it's all cylinders bad, you'll have togo through the tings common to all cylinders or pairs of them in 4 cylinder bikes...
you'll have to go back through the basics and check them off. "fuel,compression,spark " - fuel supply, carbs or even "out there" as the charging regulator has failed(check for voltage at the battery being above 14.8 and "jerky"-that'd be AC voltage which won't run the bike at low speed and is very jerky-headlight will also flare as revved)......

 

[Guest]

O gee what a drag...sooty plugs are usually considered to be overrich air-fuel -that said, it's really pretty common on old bikes diagnosed in a shop while idling a lot...a long run is what these "plug diagnosis" refer to and it's assumed the bike is running ok , so the fix is offered to use a hotter plug. But do check you are running good, correct plugs of course.... It might be you are missing sparks (sigh)
... running rough all the time is the bad one- DO check all the cylinders are firing. Often bad lowspeed is a missing cylinder-you can tell easily by starting the cold bike and checking the warmth of pipes.....needn't say don't burn yourself. If it's missing cylinders, that's a big clue. If it's missing a pair, that's a clue.

if it's all cylinders bad, you'll have togo through the tings common to all cylinders or pairs of them in 4 cylinder bikes...
you'll have to go back through the basics and check them off. "fuel,compression,spark " - fuel supply, carbs or even "out there" as the charging regulator has failed(check for voltage at the battery being above 14.8 and "jerky"-that'd be AC voltage which won't run the bike at low speed and is very jerky-headlight will also flare as revved)......

Thanks for the to do list! I will go through the following:
* Check plugs / replace as needed
* Check cylinders (both firing)
* Voltage check
* Compression check
* Spark check
* Fuel check

I will post back when I cross all the things off!

 

[Gorminrider]

I just finished reassembling with a float height at 26.2 on each side,

I know the spec sheet posted says this but it's notably a lot more than my gsx400 or any other bike on the sheet....not saying it's wrong but it reminds me per your issue.
On my bike, This would make very lean running and my bike wouldn't even idle. Perhaps you have brass floats that are heavy? But whatever, do check that the bowl gasket is off when measuring and that BOTH carbs are correct.If one is a fair amount different, on a twin, you won't get the bike to idle on both cylinders...

Your specific symptom does encourage doing this...ie:no idling. If your idlemix screws are having no effect, again, beyond cleaning,(see the recent thread https://www.thegsresources.com/_foru...pilot-jet-plug specifically there's a tiny passage between main and idle wells....) the float height could do it.

 

[Guest]

I know the spec sheet posted says this but it's notably a lot more than my gsx400 or any other bike on the sheet....not saying it's wrong but it reminds me per your issue.
On my bike, This would make very lean running and my bike wouldn't even idle. Perhaps you have brass floats that are heavy? But whatever, do check that the bowl gasket is off when measuring and that BOTH carbs are correct.If one is a fair amount different, on a twin, you won't get the bike to idle on both cylinders...

Your specific symptom does encourage doing this...ie:no idling. If your idlemix screws are having no effect, again, beyond cleaning,(see the recent thread https://www.thegsresources.com/_foru...pilot-jet-plug specifically there's a tiny passage between main and idle wells....) the float height could do it.

This is very interesting. I do have the brass bowls in my carbs. I plan on taking the carbs off tonight and I will look closely at those plug on the pilot jet as well as my float height.

 

[Gorminrider]

it's the little passage between main and idle "wells" that is super important...(I think later mikunis got rid of it and the plugs)If you look at the manual's diagrams it's very informative...and with carbs out you can blow throw the idle passages from the airbox side : You have to pull the main jet needle and idlemix screw out, plugging all the various holes with your fingertips except one...until you can actually hear a tiny bit of air at the last tiny hole under the idlemix screw where the idle mix enters the intake...On old carbs, I wouldn't expect both the be exactly the same at that little hole but air should go through nearly the same. a 1/2 turn of the idlemix should take care of any difference.

Brass floats would explain the higher float spec, so follow the specs (read the manual- but usually, bowl gasket must be removed to measure.) Probably brass is harder to shape as efficiently as the plastic ones and so are heavier per the airspace they contain... DO shake them in case they are leaking with fuel inside.

 

[Guest]

it's the little passage between main and idle "wells" that is super important...(I think later mikunis got rid of it and the plugs)If you look at the manual's diagrams it's very informative...and with carbs out you can blow throw the idle passages from the airbox side : You have to pull the main jet needle and idlemix screw out, plugging all the various holes with your fingertips except one...until you can actually hear a tiny bit of air at the last tiny hole under the idlemix screw where the idle mix enters the intake...On old carbs, I wouldn't expect both the be exactly the same at that little hole but air should go through nearly the same. a 1/2 turn of the idlemix should take care of any difference.

Brass floats would explain the higher float spec, so follow the specs (read the manual- but usually, bowl gasket must be removed to measure.) Probably brass is harder to shape as efficiently as the plastic ones and so are heavier per the airspace they contain... DO shake them in case they are leaking with fuel inside.

I have the carbs removed and cleaned them thoroughly. Using canned air I tried what you mentioned above with success. I'm glad you mentioned the plugs not being a thing in later carbs because in mine they are not. I think the last thing to do before putting the carbs on the bike would be to verify the float height. As opposed to getting terrible particular on float height, should I instead ensure they are the same and check the height using the clear tube on the drain plug trick? What is the ideal level below the seam of the bowl if I go that route.. The carb rebuild guide does not say, but the picture shows something in the range of 2.75 mm below the seam if I remember correctly...

 

[Guest]

I just wanted to update before anyone else posts, it may help you.. and me. Carbs are clean, I blasted cleaner through each passage with success. I forgot about the cart on BikeCliffs site so i went back to that, set my float to 26mm from the surface without the gasket, and tried the tube method to verify float height. The chart states. 6.5 mm below the gasket surface and I am right on the money. I feel very good that the carb is clean and set correctly.


Next I will verify my plugs and my point gaps. If all is good I will reinstall the carbs and fire her up. Hopefully it starts right up and runs well so I can verify both cylinders are firing and then check voltages at different points and finish with a vacuum sync. I'm assuming if I get that far, then all will be will from that point forward and I'll be back on the road. STAY TUNED.

 

[Guest]

Alright .. all back together ... Fires up, I can't get it to idle (let it idle no issues for 10 minutes) when I touch the throttle it boggs down... If I slam on it and get past 4k RPMs then it work... I can ride it if I keep it over 4k but otherwise it stutters and dies. Plugs always look black and sooty. I tried moving the needle clip as a last ditch effort and it won't even start on anything other than the 3rd position.

I have verified my gaps, voltages, float height / fuel level, compression, I have good fuel flow, and have the filter in the tank nice and clean and installed an in line filter because my tank was pretty rusty... I used evaporust to clean my tank and that worked well but in the past I had rust chips in my carb so I installed the second filter...

I'm totally stumped why it won't just work... I still feel like it's got to be an issue with my carbs but I don't know what to do because I haven't changed anything performance wise and it ran great before I let my brother ride it so I haven't changed any jets or anything but I'm thinking i may need too?

Is it possible that it worked before because it was tuned to work with some failing condensers and points and cracked intake tubes and now that I've fixed those things I need to re-jet?

 

[Guest]

Typo* at the beginning I said I can't get it to idle and I actually can and let it idle for 10 mins*

 

[Gorminrider]

The problem is your brother. You must kick him really hard in the shins and ask just what the heck he did to your bike! Put diesel in it?
Generally, it's the simple thing nobody bothers to mention. Also common is in the neighbourhood of the last thing done to the bike before trouble. (your brother...time for the cattle prod and the hard wooden chair!)

Have you read the concurring thread about "advance mechanism springs" ?(https://www.thegsresources.com/_for...400e-manual-spark-advance-electronic-ignition)
Did you read UKjules thread per his 250? turned out to be a ground. https://www.thegsresources.com/_for...ng-down-gsx250e-after-a-mile-always-and-stops
When ideas run out I've had to go and sit in the garden for long periods until some new idea occurs and I can return to the fray hope rekindled...! unfortunately it can take a few of these until The One pops in.
- Is the Choke/Enricher functioning? Is it pulling both the shafts of the choke pistons in and out?
-Have you ever tried riding it with the petcock on prime? (The float needles should have no trouble holding back without the vacuum mechanism in play.)
-The fuel filter shouldn't bother it -but if your tank filter is ok I'm not sure what it does beyond adding clamps to the fuel line and many people distrust them.
-Is it possible the airbox rubber collar is folded a bit and blocking the idle mix intake jets?
Does one exhaust pipe get hotter sooner than the other when starting? (I mentioned that previously)

 

[Guest]

You ain't kidding, my brother does deserve a beating now

* The choke plunger functions fine, moves freely... I will admit one of my choke plungers doesn't have the rubber boot at the top.. the first time I cleaned the carbs I had lost it... Would that do it? I hadn't thought of that until now...
* The additional fuel filter was because the one in the tank was getting plugged up quickly with rust flakes, but a good flow of fuel is still being delivered to the carbs..
* I'll check the intake boots that's in interesting thing I hadn't thought of..
lastly.. * the pipes both get warm and both cylinders are firing...

I swear if I did this to myself over that little choke plunger boot idk what I'll do lol

 

[Gorminrider]

Your bike seems to idle fine..and anyways Boots on choke plunger shouldn't bother it too much but you can pack some grease around them temporarily to see if they are letting massive amounts of air in when they are closed(choke off) but I doubt it.

Got it home, the pin in the carb was stuck in the venturi part so I took apart the carbs. They were gross.. cleaned them (ultrasonic in carb cleaner) re assembled with new rubber.

"pin stuck in venturi" doesn't sound good...and that would ring my bell...but
Your symptoms seem to centre around that period between idle and "lifting" the jet needle from the high speed jet for higher speed. It could be several things per the carbs- the actual idle jets always come to mind because they're most important from low to midrange whereafter the mainjet dominates. You have to entirely remove them(lowspeed and highspeed jets) from carbs to clean them. I hope you did.
if you are finding particles of rust in the fuel, these are going to dirty the tiny holes in the idle jets and it might take cleaning more than once...If adjusting the idlemix screws isn't having any effect, the idle jet is a suspect beyond the screw itself with its tiny hole, rubber o-ring ,washer and spring.
.....When you are thinking about the idle and choke circuits on these CV carbs at startup, the throttle plate isn't open but the pistons/valves are sucking very hard. IE: high intake manifold vacuum. That's why these circuits have such teeny holes when they put mix into the intake side of the engine...lots of suction at the intake. Up to here, your bike seems ok...but ideally now that the motor is spinning, as you open the throttle plate, more air is allowed to flow over the other jets in the carb bore allowing more gas into this airstream so the engine goes faster and maintains a fast flow of air...you can sort of feel this when you blip the throttle and there's a hesitation as the vacuum drops.. .especially when idling a cold bike and even worse with choke on when it ruins the idle with too much air/vacuum reduction...(somewhat explains why not to use the throttle on start-up on these...)

That's just the carbs. It doesn't mean it can't be something else. The ignition was the starting point of the thread and I expect it's ok by now because the bike runs at low and high rpm. But a real ride test when real torque and power is needed is always the final arbiter.

 

[Guest]

So what I meant in the earlier post is the Needle jet (pin) had lifted from it's seat in the emulsion tube (I think) and missed when it came down.. it happens when I flip the carbs upsidedown, is that not normal..?