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Discussion Starter #1
2001, 1100.
I have the carbs off to clean them. The jetting is stock, including the PMS screw still has the cap.

I'm wondering if the previous owner should have jetted when putting on the exhaust. I'm not sure what brand exhaust it is, but in addition to the change, the baffles have been removed.

The air box is stock.



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... I'm wondering if the previous owner should have jetted when putting on the exhaust...
I would do a plug chop at idle, 1/4 throttle and 1/2 throttle... you can probably feel if the bike is running lean above 1/2 throttle.

Incidentally the term "plug chop" has gotten to be a literal meaning in some circles but really all you want to do is run the motor under load at a particular throttle position and then pull in the clutch, immediately turn the ignition off and read the plug condition.
 

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If you have an aftermarket exhaust you need the proper jets to match.

Stock bikes from the factory are setup to get the best possible mileage and lowest emissions. If you change the intake air cleaner, the exhaust, the cams, pistons... then you have changed the jet size required for the proper fuel ratio

An engine will tolerate running a bit rich, but running lean raises the temperature in the cylinders and the heads.

EDIT ADDED: if you essentially have straight pipes with no baffles, you should be able to find a table with the right jet size to use, even though you dont know who made the exhaust.
 

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Looks like stock head pipe with slip on mufflers. No rejetting should be necessary. Might need to turn PMS screws out about 1/4 turn if you are getting any popping when closing throttle at speed, doesn't take much. Follow link for jetting recommendations.

https://sites.google.com/site/vstar1100kb/home/tuning/carb-jetting

Here's a snap shot of jetting recommended in link.

 

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Discussion Starter #6
What is the other jet supposed to be stock?
Mine is 42.5 .

And are the little spacers significant?

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Looks like stock head pipe with slip on mufflers. No rejetting should be necessary.
Les, he said the mufflers have no baffles, he is running straight pipes with no resistance

I'm not sure what brand exhaust it is, but in addition to the change, the baffles have been removed.
I don't know how to read that table.
 

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There is not a 42.5, did you possibly read 112.5 for 42.5? It's small print and sometimes not real clear. Other that the main jets all others are not needed to be changed. Yes, the spacers are important. Read the link for for detail. Here is screen shot.
 

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I have always followed
https://sites.google.com/site/vstar1100kb/home/tuning/carb-jetting
Which was suggested to me years ago. I've had stock exhaust, drilled, open and currently Cobra Slash Cut full exhaust. Other the turning PMS screws out to eliminate popping I did not change jets. Had great throttle response with out any driveabilty issues. The only time I have to up the jets was when I put KN filter in. When you put more air in it will take more fuel to maintain the correct air/fuel ratio, which should be close to 14.7 to 1. The chart is set up the left column is which intake you have, next column is exhaust, follow down till you find your setup, then over to right to find correct jetting and PMS settings. It basically says with stock intake with any exhaust the only change needed it PMS adjustment. My personal experience is exactly that. I had to read the article I linked several time till I understood it. Guess I'm getting old and comprehension is not what it used to be. I have worked on Holley, Carter and Quadujet carbs for many years. The Mikuni carbs are very simple and we try our best to make them complicated. Trust the link. If the recommendations don't work 99 percent of time there is another issue, vacuum leak, clogged jet, etc.
 

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Discussion Starter #10
I realize the PMS cap needs drilled for the adjustment.
But those are the makings on the jets indicated


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When you said 42.5 I thought you were referring to the main jet. Here's an excerpt on jets.

Note:
The carb has 2 "main jet" sort of items in the float bowl. One is in the area of 110ish and one is probably a #42.5. The #42.5 is the jet that controls the choke circuit and normally, you don't change that one.

Hope this helps.
 

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2001, 1100.
I have the carbs off to clean them. The jetting is stock, including the PMS screw still has the cap.

I'm wondering if the previous owner should have jetted when putting on the exhaust. I'm not sure what brand exhaust it is, but in addition to the change, the baffles have been removed.

The air box is stock.



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stock pilot jet is 17.5 main is 115, and 112. if you only change exhaust leave the pilot stock. you can increase themain to 115 in both cylinders. that way you only need to buy one mains can be bought from local harley shop. ask for round small head. if the intake is stock you are not increasing any air so you dont have to raise fuel .the pipes will pop on decell so raise the pms setting a quarter turn.. sorry if i'm rambling . the upshot is just turn the pms screws out a little... read all the links on jetting they will explain
 

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Discussion Starter #13
I've been reading them. I was thinking of putting the 112.5 in the other carb and putting a 115 in.

But first i need to figure out why my bike seems to be running on one cylinder. I thought it was a carb issue, but they weren't very dirty.

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the mains are fine, put 115 in both carbs.did you clean the pilot jets including the small holes on the sides. can you see light thru them when looking thru end to end.with only a pipe change just turn the screws out a bit.pull the plugs what color are they. are they both sparking. drain the float bowls see if they both fill up when you turn the key on. could be a blocked fuel line
 

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Discussion Starter #15
I cleaned the pilots.

The bowls do fill.

The idle sucks now.

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Discussion Starter #16
A week ago it ran fine.
The next day it was sluggish, but would surge quickly. I think one cylinder is dead, but comes back for a second.
Front plug was black, but not wet.
Rear was tan and nice.


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If you did get the carbs good and clean then change that plug. It's gotten fuel fouled. Should fix issue. Plugs are too cheap for me to clean right and reuse.
 

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https://docs.google.com/file/d/0B-KrKk_YXL4Tdm5OU1I4S2pMUFE/edit heres another link for the inside of the carb. with pictures.the rear plug is close to normal but the front is wrong.
you dont know what the po did so check everything.what size jets, are they in the right spots. how many washers on the needles. are the needles held in there holders.

under the top 'big' black cap is a small oring ,check the diaphram for cuts, blow out all the passages.
leave the float alone but it may be off. "float is tricky"
 

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A week ago it ran fine.
The next day it was sluggish, but would surge quickly. I think one cylinder is dead, but comes back for a second.
Front plug was black, but not wet.
Rear was tan and nice.


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that fron't cylinder is past running rich, look,s to me like it,s flooding,could be the float needle hanging up, or maybe the slide sticking and hanging the jet needle, the main jet doesn't come into play until your past 3/4 throttle. so i doubt the main is the problem. if the problem was in the choke circuit both plugs would foul so that's most likely ok, what's the compression in the front cylinder ? maybe it's not even firing from a bad spark or low compression, always start with a compression check because if it's too low all the tuning in the world won't get it to run right
 
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