Weird gas problem

[jwhite2]

So I FINALLY got it running tonight.  I noticed something when revving the engine.  The right side is fine, revs normally.  The left side, however, only slows when I pull in the throttle and then jumps up real high when I release it.  It comes back down normally, so I am assuming its some kind of fuel delivery problem in the carb that causes a back up of fuel and then a rush.

Any ideas?

[jwhite2]

This might help out.  See if you can tell from the video.  Sorry its REALLY blurry.  Not sure why the camera did that!

[reed]

jwhite2
On your carb problem take the carb off the motorcycle,strip it down  and check the float level.
Then go on and remove the pilot jet and clean,do the same remove the main jet and clean.
With the jets out and the float assy out blow the carb out with air then rebuild etc
Try that Thanks.
Steve.

[jwhite2]

Gonna try that today Steve.  I figure it has something to do with that carb but im no master on how they work so ill just do a complete cleaning again.  Well see what happens. 

Thanks,
John

[jwhite2]

Took the left side carb apart today for cleaning.  Also, removed and cleaned the exhaust a bit.

Ive noticed that the left side is NOT firing.  Just my imagination before.  In the video it looks like it is. 

Still no clue on this one.  Question though.  With the petcock fully open (which is down I think, clarify if im wrong) I dont get just an amazing amount of gas flow out of either side.  I feel like the petcock needs to come off for another cleaning but I have already done that.  I dont know how dirty these things could get.  The inside of my tank is mostly clean.  Im just not getting that flow like I do on my 90 sport.  That thing just gushes gas out.  The one on my MKII is just barely dripping at best.  But its good enough for the right side to fire?!?!?  So im not sure whats going on.  Someone help!

John

[OldSwartout]

Definitely clean the petcock before you do anything else.  It should run a steady stream from both outlets when on (straight down).  Reserve is straight forward. Make certain it is working too.You may need to run a drill bit through all the passages and poke a wire down the brass standpipe.  If you are getting low flow, it will feed one side and not the other, plus you risk causing the side that is running to go lean and lead to seizure, if you tried to run it hard that way. 

[scrambler]

I'm still thinking points.

[Toystoretom]

How are you throttling the carbs up? It looks like you are pulling on something and then the left cylinder fires for just a second (because a little smoke comes out the left muffler). Possibly the throttle stop on the left carb is set too low and that side doesn't fire until you open the throttle just a bit. You may need to sync your carbs just a bit so both are open the same amount at the closed throttle position (in other words, at an idle) and adjust the cables so both carbs open at the same time when you twist the throttle.

Your carbs should idle by using the idle circuit and I have to wonder if that is clogged on the left side.

You could take the petcock issue out of the equation by using a remote gas tank setup. Get a can or plastic bottle and run down to the hardware store and get some fittings you can install into the can (or bottle) and run your fuel lines to that.

[Toystoretom]

Here is a trick... but be careful. If both sides are firing the exhaust pipes on each side will be hot. You can put your hand close to them and feel for heat coming off of them (Don't actually touch them, you will burn your hand). If a cylinder isn't firing the pipe will be cold compared to the side that is firing.

If you have a timing light you can put it on the plug wires while the bike is running just to see if that wire has spark.

Your gonna burn that shed down...

[scrambler]

If I think a plug isn't firing I pull the wire off the plug while its running. If nothing happens, that cylinder wasn't firing.

[moonpup]

If I think a plug isn't firing I pull the wire off the plug while its running. If nothing happens, that cylinder wasn't firing.

That just doesn't make any sense.  

If one cylinder on a dual cylinder bike isn't running because of fuel starvation, merely pulling that spark plug wire (whether it's firing or not) won't tell you anything. And on the other hand, if you have fuel but no spark, you'll still have the same results with just pulling the plug wire.....nothing.

If you think a plug isn't getting spark, stick a screwdriver in it and check it the old fashioned way.

[jwhite2]

Its getting spark and fuel.  The plug is wet but its not firing.  So I guess that only leaves compression as the culprit?  Im still worried about the petcock.  I feel like gas should be flowing a little more freely than it is but if one side is running fine then I guess its ok.

I just dont get how I have good compression in one cylinder and bad compression in another?  Maybe someone tinkered with one side of it?

[scrambler]

I'm not talking fuel problems here. Only spark problems. If you suspect a spark problem but are not sure you can pull the wire. If it continues to run just like it did before you pull the wire it confirms that you were only running on one. If the bike sounds different when you pull the wire it was actually running on both.

It actually is more useful on 4 cylinder bikes.

[scrambler]

I watched your video again. I don't think it was ever firing on the left.

Are you 100% sure you have spark on the left?

[reed]

jwhite2
Go on the back to basics forum and it will help with doing a compression test.
And a spark test then let us know how you get on and there will members on
The site will help you!
Thanks.
Steve.

[jwhite2]

I know for sure ive got spark.  Brand new spark plugs and when I pull em and put them on the cylinder it lights up bright blue when I kick it.  Ill check in on the compression test.  Might go down to Oreilys and just grab a gauge this afternoon.  Probably need one for the future.

[jwhite2]

Checked compression on both heads.  About 140 - 150 PSI on each head.  Its not compression.  Ive cleaned the carbs twice now.  Im getting spark, im getting fuel to the plug.  What am I missing?

[old smokey]

A little hard to tell in the video, but I think you have black fuel lines, right? Get some clear (or blue or yellow) fuel lines and then you can see if there is fuel in the line on both sides. Looks to me like only 2 short bursts of the left side firing in the video.

[Toystoretom]

If you have spark (and it is even somewhat close to being in time), fuel, and compression, it ought to at least fire or hit every once in awhile. Except that this is a two stroke...

Compression tests on these can be misleading. Good compression only shows that the piston is going up and down and the rings are sealing. The trouble is that you may be compressing the same air that is in that cylinder over and over, no fresh fuel/air mixture is being sucked in and no spent exhaust gas is being pushed out. You may have a bad outboard crank seal on the left. If the seal between the two cylinders was bad it is unlikely either cylinder would fire.

A crude test would be to take off both engine covers over the carbs, hold the throttle wide open, with the ignition off kick the bike over and put the palm of your hand over the mouth of the carb. If the crank seals on the side you are testing are good, you will feel a strong suction. If they are bad you will feel very little or no suction. The right side is obviously good or it wouldn't fire, so compare the left side to that.

Maybe someone can provide a link to a good explanation on how a two stroke fills the cylinder with a fresh fuel/air charge, and why it is important that you have good crank seals on each cylinder.

I'm not saying that this is your problem but it's starting to look like it.

[jwhite2]

Ill check on the clear fuel lines.  Those were just what Oreilys had at the time.

Would I be able to hear the air going into the cylinder?  Because I can definitely hear an airy suction noise if I turn the motor over one piston at a time, slowly.  I will try removing the left side case cover and do the suction test as well.  I can hear something though.  

Notice how in the video, that left side seems to "fire" or something when I pull the throttle.  At least, exhaust comes out so I assume that.  It no longer does that.  Cranked it up yesterday and didnt get that again.

On a different note, once this thing is running well and on the road, what kind of speed can I expect out of a MKII RS?