Motor bogging at mid rpm

[Ryanmelton69]

I have an 86 r and it runs great at an idle and low rpm. After the quad is warmed up and ready to rip, it bogs down at mid rpm ranges. It is almost as if its air/fuel mixture is not adjusted correctly or something. I changed the gas (40:1) and changed spark plugs. I adjusted the air/fuel mixture and took the carb apart (which is spotless). However, it still bogs down before it even hits its powerband. Does anybody have any ideas about what is wrong? Could it possibly be the jets, reeds, or the electrical system?

[C-LEIGH RACING]

Could be crankcase puddling fuel & when you get on the gas its loaded up kinda like its flooded.
Pull the carb back off & tell me what size jets are in it, & what has been done to the engine, porting, big carb, what type of air filter.
Try setting the plug at 18 to 20 thousanth, those old stock ignitions are weak & sometime wont spark across a wide plug gap.
Neil

[Ryanmelton69]

The main jet is a 176, or around there. I had it off a little earlier and looked at it and cleaned it out. The engine has after market reeds and a K&N air filter. I also have a paul turner race pipe. I just bought the quad and all of these came on it. I have talked to a couple people and they think I may need a larger jet.

How would do I tell if the fuel is leaking into the crankcase.

[PYF]

Originally posted by Ryanmelton69
The main jet is a 176, or around there. I had it off a little earlier and looked at it and cleaned it out. The engine has after market reeds and a K&N air filter. I also have a paul turner race pipe. I just bought the quad and all of these came on it. I have talked to a couple people and they think I may need a larger jet.

How would do I tell if the fuel is leaking into the crankcase.


176 Seems high for that setup...Most of the setups like these I saw, they were running 165 Main...

By the way...Mid-Rpm bogs is usually the needle if I'm not mistaken

[Ryanmelton69]

I will have to buy a jet set. Off note...what are the carb adjustments supposed to be set at?

[beerock]

you need to do some plug chops and get the main dialed in first then play with the needle

[firefighterjosh]

I would adjust the needle. I would put the clip up a notch. Try it. If it still does it repeat the step. If it gets worse go the other direction.

[Ryanmelton69]

How do I adjust the needle. Just to verify, you are talking about the needle from the throttle cable?

I just put the motor back together (I had to fix the clutch lifter lever) and since then it runs like ****. I think it is the carb, but it takes a whole bunch of kicking to get it to fire, and then it wont idle at ALL. I tried adjusting the gap on the plug but it made it run worse. Any ideas? I may just buy a new carb. I have heard great things about the keihin 38mm, any suggestions on a good site to buy one for cheap?

[firefighterjosh]

the needle is located in the carb. If you take the cap off the top of the carb the needle will come out with it. There is a way to get ot off the cap (I have never looked at a r carb) and the needle will have a clip on it. Just move that clip up or down

[Ryanmelton69]

Thanks, I will have to try that. Do you know how many turns outward it is for the air/fuel mixture?

[firefighterjosh]

Nope, I only know the basics. Sorry

[lee37vernon]

how to set up your carb !!!!!!!!!!!!!11 (http://www.atvriders.com/articles/jetting.html) :Dand another .... (http://www.motocross.com/motoprof/moto/mcycle/carb101/carb101.html) and more ... (http://www.duncanracing.com/techfaq/Tech_keihin-carburetion-jetting.phtml) [...........[/URL] how to read a plug ....! (http://www.motocross.com/motoprof/moto/mcycle/plug2/plug2.htm)


here is a list of what the numbers on a needle stand for ..
Re: needle chart
--------------------------------------------------------------------------------
Here are the specs from kehin

Here is how to read a Kehin needle

the first letter is the needle taper, the second is lenght the third is diameter.

a BGK needle is 1.15 degree of taper
39.6 mm is barrel length and .69 mm of diameter.

Taper
A = 1.00 degrees ... leanest
B = 1.15
C = 1.30
D = 1.45
E = 2.00 ... Richest

Length
G = 39.6 Leanest
F = 38.6
E = 38.1 Richest

Diameter
Q = 73 Leanest
P = 72
M = 71
L = 70
K = 69
J = 68
H = 67
G = 66 Richest

hope these help ;)

[C-LEIGH RACING]

You still havent said what size the slow jet is in that carb.
If the right size slow jet is in the carb for the type of engine build you have it will idle if thats how you want it.
Most times the slow jet adjustment screw will be turned out 1 1/2 to 2 1/2 turns out depending on where the slide is set at for a smooth idle speed.
The old PJ carbs, the idle adjustment is located in the choke plunger & will have markings on the carb body at the choke to indicate that.
The PWK model carbs will have a screw in the slide area to set the idle speel.

If you thinking changing jets is a real easy task, you will need to rethink. The main jet in a Kehein carb is somewhat easy to change & the slide needle, but the pilot jet, & the inlet float needle setting, the carb will need to be removed from the engine to do it properly.
Neil

[MR.BIG]

If its a midrange bog it is definately the needle. You make it sound like its lean so move the clip on the needle down to richen it up if its to rich move the clip up.

[Ryanmelton69]

Would running it too lean make it bog down like that? I am thinking that it is more the high end throttle. It doesnt hit the power band, but I am planning on trying several new main jets. It has a 176 in it now and from what I hear its pretty high. I will mess around with it tomorrow and try everything. If the needle is adjusted wrong would it really cause it to not hit the high end or the power band?

[firefighterjosh]

Originally posted by Ryanmelton69
Would running it too lean make it bog down like that? I am thinking that it is more the high end throttle. It doesnt hit the power band, but I am planning on trying several new main jets. It has a 176 in it now and from what I hear its pretty high. I will mess around with it tomorrow and try everything. If the needle is adjusted wrong would it really cause it to not hit the high end or the power band?

Your Needle does your mid range and the main jet does high end. Adjust your needle or Main Jets from what is bogging. And yes a too lean can bog your motor.

[Ryanmelton69]

I am going to mess around with the jets tomorrow. Its not really like its bogging down, more like its being cut off of fuel.

[321racer]

if none of that works
take of the flywheel cover and look at that
the same thing happened on mine....... a little water got into it somehow and rotted the wire that goes to the flywheel pickup and thats exactly wat was happening to me.
id try that if nothing else works
goodluck!

[Ryanmelton69]

Thanks for everyones help, I rejetted it from a 178 down to a 155 for the main. That practically solved the problem. Its running a little lean on the top end so I will most likely switch it up to a 158 or 160. Once again, thanks for your help!

[beerock]

Originally posted by beerock
you need to do some plug chops and get the main dialed in first then play with the needle

yes, now once you dial in the main THEN you can play with the needle... ;)

glad its running better for ya