79' XS400-Winnipeg

Yes below tolerance.

Installation of clutch Pittsburgh done with relative ease. I will say the Kickstart was complete other problem. Extremely finicky.

I have a reoccurring problem and I'm believing it's fuel or air mixture. Every time I go to hit the gas anything over 3000 RPM there's a lag and sputtering of the engine.

I have the carbs cleaned this summer. And stock Jets put in. I have an aftermarket exhaust but I don't think it's that.

Any ideas before I rip the carburetors clean them again and get new Jets
 
Long story short, I installed the mufflers that I would tune the bike to, also using the stock air boxes.. My bike was jetted with 135 main jets.

Being that I have after market mufflers, I thought for sure Id need bigger jets. Well I was wrong. I went from a 135, to 137.5 and then a 140. Then I went to a 142.5 and still no improvement, but the stumbling/hesitation was there when I hit full throttle. Then I raised the needle to richen up the midrange, The bike really started to run like crap and I figured out I was way too rich. I have a whole collection of jets now! lol

So I started all over again with new 135 mains. I ended up moving down to a 132.5 and then went down another step to 130.

The 132.5 was where I started to be satisfied with the performance. Still had a very very slight hesitation at the top end like how it was when it was too rich.. So I put the 130s in and the stumble/hesitation is gone..

Ive started to get a weird popping on the left side and when the idle was really low and I believe I was getting pinging. I still thought it was a leak in the exhaust and I ended up sealing both sides and still had the problem. Come to find out, the left side was timed too far advanced.

I should mention that I have the Pamco ignition with the E-advance and the instructions say to check the timing after a certain amount of miles to make sure that the PC boards on the timing plate didnt shift out of place. I guess from all the heat and vibration they loosened up because they werent very tight at all when I adjusted them.
 
NewHavenMike said:
Long story short, I installed the mufflers that I would tune the bike to, also using the stock air boxes.. My bike was jetted with 135 main jets.

Being that I have after market mufflers, I thought for sure Id need bigger jets. Well I was wrong. I went from a 135, to 137.5 and then a 140. Then I went to a 142.5 and still no improvement, but the stumbling/hesitation was there when I hit full throttle. Then I raised the needle to richen up the midrange, The bike really started to run like crap and I figured out I was way too rich. I have a whole collection of jets now! lol

So I started all over again with new 135 mains. I ended up moving down to a 132.5 and then went down another step to 130.

The 132.5 was where I started to be satisfied with the performance. Still had a very very slight hesitation at the top end like how it was when it was too rich.. So I put the 130s in and the stumble/hesitation is gone..

Ive started to get a weird popping on the left side and when the idle was really low and I believe I was getting pinging. I still thought it was a leak in the exhaust and I ended up sealing both sides and still had the problem. Come to find out, the left side was timed too far advanced.

I should mention that I have the Pamco ignition with the E-advance and the instructions say to check the timing after a certain amount of miles to make sure that the PC boards on the timing plate didnt shift out of place. I guess from all the heat and vibration they loosened up because they werent very tight at all when I adjusted them.
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THANK YOU! dam good advice!
 
So here is yet another question.

Riddle me this. Why is the carb on the left burnt? Could it be for the jets being off (to big)?

Happy riding, season here in Winnipeg is almost done
 

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Jet sizing would be determined by how the bike feels when it runs on full throttle. Being on one side only, I dont think its related to fuel. My guess is its leftover sludge from not cleaning enough or your intake valve isnt closing all the way and youre getting a backfire into the carb. Could be from a dirty air filter too I suppose or maybe oil coming up from the crankcase recirculation tube, But it has to be something that is not shared with both carbs. Like a filter or an intake valve.
 
It's never one problem on this bike. The nik bogs down when I accelerate. So I have new jets coming for that.

Your point on it not being shared makes sense. I'll clean them both out reassemble look at the intake valve and go from their.

Never ends lol
 
Bogging down usually means too lean. Sputtering and hesitation usually means too rich. My bike, when full throttle at low rpm, will have a small bog, but I can still feel the torque its making. The bog doesnt hold rpms either, it just sounds throaty as it picks up. Its the CV carbs catching up... If that makes any sense.

You should get at least 5 sets of jets. I have 130-142.5 mains and Ive gone through all of them and tested each one and varied the needle jet on a few of them to be sure which way I needed to go. Jetting is a long process if youve never done it before.

But you might be able to take a short cut, if you have 135s installed, get 140s and a like a 132.5 or 130. Then you can narrow it down.

After doing it for a while, you kind of just know what the bike needs. You get better at removing carbs and its less of an issue. But when it finally runs well, its a great feeling.

You definitely need to upgrade from the points ignition if you havent already.. Thats a big hassle. The timing has to be pretty much perfect when youre tuning and I bet thats a problem. The right side on your bike may be firing too late. Do you have a stroboscope?
 
I have always had bogging with over jetting or rich. Bucking or surging for lean conditions. Fouled plugs can also cause these issues. I agree with the black being from a valve or past backfiring into the carbs. Make sure the bike gets the carbs synced with a manometer. One may be pulling more than the other.
 
You absolutely need a stroboscope/timing light to make sure you're timing is good on both cylinders. Tuning the carbs will be pointless if the bike isnt in optimal condition prior to jetting.

You need to make sure that valve clearances are proper, sparks plugs are new and gapped, and your timing is correct on both cylinders. I really think you are having timing issues.. Points are very finicky and are a whole 'nother set of issues. One side could be OK while the other is way out.. My bike was way off on the right side when the left was perfect.. I had timing issues even with the Pamco, but getting timing right was much easier and a lot more precise than the points.

Get a timing light and make a manometer. You make a manometer by using two beer bottles, some kind of sealant like silicone, I used hand-kneaded repair epoxy because it had a cure of like 5 minutes, and a few feet of fuel line..
 
New jets worked like a hot dam (size 130). Whole new bike with the latest work.

A very minute back fire and I mean small on the left side. I'll sort that card out this off season.

Thanks again guys
 
Question. When going with airport filters, that are attached directly to the carbs. What do you do with this hose that attaches to the river H pipe?
 

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Winnipeg_79_XS400 said:
Question. When going with airport filters, that are attached directly to the carbs. What do you do with this hose that attaches to the river H pipe?
Click to expand...

Are you talking the breather hose off the crankcase ? If so get a small filter and bolt it directly to the nipple.

I kept the H pipe for the 400 and Unis bolt to the H pipe. My 1100 direct unis on the carbs so a small filter on the crankcase breather.

Something like this https://www.amazon.com/Uni-Filter-U...d=1509390156&sr=8-12&keywords=breather+filter
 
So I have removed the left side with no issues. The right side is stuck.

I was able to remove the retaining clip, but not it feels like the cap is attached to the spring and won't pop out.

I tapped on the dampening rod but with no luck.

Ideas?
 

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So I looked on here before posting and still was not clear.

I'm looking at getting this sporster tank (attached picture).

It looks like it may only have one hose (one that connects to the carbs.

If this is the case, what do I do with the stock hose that connects from the top of the stock petcock to the intake?
 

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Need to block it somehow.
Either plug the hose or remove the hose and cap the barb on the intake boot.
 
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