I installed full Yoshimura pipe, K&N lunchbox, jetted with 40/147.5.
Started synchronizing and relized that even when the screw is all the way out, the left carbs still pulls much harder than the right one.
What may cause that?

A while ago I took carbs apart and cleaned them. Perhaps I did't put the linkage between left and right throttle right? I also was able to get them pretty close with the stock pipe, airbox and jetitng. Now the left side seems to be way way way stronger.

Jenya

You have to balance carbs at 1750 rpm exactly. This magic number is there because vacuum holes in carbs are in different sizes. The left one has a bigger hole so if you open some throttle you might think carbs are out of sync, because it sucks more.

Carb sync must be done on warm engine, at 1750rpm (use idle adjuster). And dont press on the adjusting screw, only turn it slightly. It shouldn't take longer than few minutes to adjust the screw.

Okay, I figured out the problem with synchronization. I lost the small O-ring when I was adding a washer onto the needle.
So that is fixed now and carbs synch just fine.

HOWEVER, the bike doesn't run right. it fouls spark plugs within 3 minutes of idling effectivelly rendering them useless and dying.
I mean FOULED. I had never seen such a black sparkplug. Now, I haven't actually ridden it, so I dn't know how the main jet works, but
just idling in the garage, it seems grosly off. I wonder if I should try to put back the stock pilot jet instead of this 40.

I have: Yoshi, lunchbox, 40 pilot, 147.5 main, no washer, 1.5 turn of idle mixture.

Any ideas what could be wrong?

Jenya

High floats ... like waaaaaay high ...
Cool.
Srinath.

Quote from: domas on September 24, 2006, 10:51:01 PM
You have to balance carbs at 1750 rpm exactly. This magic number is there because vacuum holes in carbs are in different sizes. The left one has a bigger hole so if you open some throttle you might think carbs are out of sync, because it sucks more.

Which holes?

Is this why I have seen posts of different sized main jets?

Ex: http://gstwins.com/gsboard/index.php?topic=11798.0
And, this guy used to have different sized mains as well, but unfortuneately the information is lost: http://gstwins.com/gsboard/index.php?topic=15475.msg135551#msg135551

Quote from: scratch on September 26, 2006, 08:15:53 PM
Which holes?

Is this why I have seen posts of different sized main jets?

Ex: http://gstwins.com/gsboard/index.php?topic=11798.0
And, this guy used to have different sized mains as well, but unfortuneately the information is lost: http://gstwins.com/gsboard/index.php?topic=15475.msg135551#msg135551

The vacuum hole on the left carb is used for sucking the petcock and there goes a hose for that purpose. The right one is normaly closed with the rubber cap. These two holes are in different sizes. I had to use different diameter pvc hose to fit on both. Also after adjusting carbs at 1750 rpm, and giving it more throttle, makes readings go mad and show that carbs are out of sync. So the only reasonable explanation i could come up with, that the holes for adjusting carbs are in different sizes. If they were the same, then the magic number wouldn't be needed.

And for those different main jet sizes for older models, is because the exhaust pipes are longer for left cylinder. So to compensate this they made jets uneven. This was solved somehow later, and now we have even jets. Maybe the changed the diameter of the header pipe, dunno 

Quote from: seshadri_srinath on September 26, 2006, 08:06:01 PM
High floats ... like waaaaaay high ...
Cool.
Srinath.

And yes +1 on that.

After adjusting floats set your idle screw to more turns.

Quote from: Jenya on September 26, 2006, 06:46:05 PM
Okay, I figured out the problem with synchronization. I lost the small O-ring when I was adding a washer onto the needle.
So that is fixed now and carbs synch just fine.

HOWEVER, the bike doesn't run right. it fouls spark plugs within 3 minutes of idling effectivelly rendering them useless and dying.
I mean FOULED. I had never seen such a black sparkplug. Now, I haven't actually ridden it, so I dn't know how the main jet works, but
just idling in the garage, it seems grosly off. I wonder if I should try to put back the stock pilot jet instead of this 40.

I have: Yoshi, lunchbox, 40 pilot, 147.5 main, no washer, 1.5 turn of idle mixture.

Any ideas what could be wrong?


Ok fix your float height then see what happans. If it's still rich drop down to a 142.5 main.

I have the EXACT same setup as you and I'm running 142.5 mains, 40 piots, 2.5 turns out, zero #4 washers.

My float height is correct and my carbs are synched
Jenya

The float levels were set properly. I checked with clear tubing and the level was around the gasket.
I don't see how dropping the size of the main jet would help plugs getting fouled while idling.
I put back the stock 37.5 pilot and the bike ran great. Took it for a spin. No problems at all. Got home, pulled the spark plugs, not fouled a bit.
I reilize that perhaps 37.5 is on the lean side, so I am thinking going somewhere in between 40 and 37.5.

On the side note, I like the responsivenes the bike acquired with the Yoshi pipe and lunchbox. Much better than the stock setup. However, I find the noise coming from the Yoshi rather obnoxious. Especially when opening the throttle and the engine is under heavy load. From low rumble it goes into LOUD rattle.
Do other people experience the same behavior?

Also, whenever there is any engine brakeing, I hear popping sounds from the pipe. Like a mild backfiring. I didn't seem to hear any of those with the stock pipe. Is it something I should be concerned about?

Jenya

popping usually means lean.  a little is no big deal, but a lot should be checked out.  Remember, everywhere else in the world had 40's stock - only in the US was it used, so 40's in themselves wouldn't blacken your plugs as you describe.  You sure you have the non bleeder jets and not the bleeder ones? 

part #'s
http://gstwins.com/gsboard/index.php?topic=6911.msg57663#msg57663
discussion on the different types
http://gstwins.com/gsboard/index.php?topic=3252.0
http://gstwins.com/gsboard/index.php?topic=4532

yoshi's sound like that up top.  different pipes sound different especially under full load and higher rpms.  I find the metal ones are the loudest, while the carbon ones are a little more mellow.

good luck - almost there!  you're close to enjoying your new setup.

Ha, I had no idea there are bleed and no-bleed types.
You see, the origional 37.5 pilots that the bike came with, apparently, are bleed ones. They have holes in the sidewall.
Therefore, it did't even occure to me that the 40s that I bought from the dealer, that also had holes in them, may not be the right ones for the job.
It all makes sense now.

The question I have now is, is it worth of getting 40 non-bleed instead of 37.5 bleed?
And if I do use bleed jets ( I think they called them emulsional jets at my dealer and they only have those), which size would be appropriate. Obviously, 40 is way over the top?

Jenya

Domas - Thanks! 

Well, I did some research on the bleeder vs. non-bleeder pilots.
Accoding to seshadri_srinath, 37.5 bleeders are equal to 40 non-bleeders.

Well, the bikle runs great with 37.5 bleeders, so I don't know there is any point in replacing them with 40s.
I think I will just ride and enjoy the last few weeks of the season. Will monitor the state of my plugs for sign of
anomalities.

Thank you all for your help.
Jenya

The originals were not bleeders.  They look just like the non-bleeder 40's.  Someone probably replaced them.  However, you should be fine now.

popping with our exhaust when decelerating is normal. I get it to. It's post combustion ignition of fuel in the headers.

the loudness is normal too. I'm not too fond of it either. Sounds a bit like a fart can. 

But the power gain is noticable. 

37.5 bleeds = 40 non bleeds, and no one seems to take that statement the right way ... So here goes ...
If you have bleeds and 37.5's are working, leave it alone.
You may want to try 150's since you suspect 37.5 is a shade lean. Upping mains will richen the low end just enough to cover you in case you are lean.
Popping is'nt common on shut throttle, but when you shut throttle it does do that sorta back draft thing ... that is common - where the bike is driving the motor and not the otherway round.
Cool.
Srinath.

Yeah, somebody before me definitelly fiddled with the carbs, and installed bleed 37.5. They also added a washer unter the needle. In the process of putting everything together, they managed to pinch the edge of one diaphragm with carb's top cover. Fortunately the diaphragm  didn't develope a leak.

Bike runs great with these 37.5 bleeds. so I think, indeed, I will leave it alone and simply ride.

Yeah, the improvement of the power and responsivness of the throttle is unmistakable. It isn't even remotly subtle.

Jenya