Updated Carb Question

Posts: 96

Hello,

I am posting a new thread to refocus my questions. So I have figured out most of the 250's dont use the same carb as the Joyner stock, and they sometimes upgrade to the 32MM which comes on the Joyner. Let me know if I am wrong on this.

The dealer (Fast Freddies) where I bought my Joyner said they tested many main jet and air filter combinations on the SV250 over the years and my 137.5 Main Jet is the correct one for SoCal usage from sea level to about 4000 ft. He said they are tempermental to changes in air filters or pop because the fuel line gets clogged, or dirt gets in the carb. And I have to say his thing ran perfect for a few months just as it is.

It didnt start the popping until I put the bigger spring and 17g sliders in it and went from the K&N attached right to the Carb (which fell off and I lost it) to the stock elbow with a Larger K&N on the end. It had fallen of before and never popped with an open carb. I dont know how long I was driving when the airfilter popped off but it ran fine on the way back to my trailer. I have since cleaned the carb and its popping worse than ever. It has warmed up some, but not really because here in the desert it goes from the 40's to 80's in a few hours.

The Pilot screw on my Carb as been stuck since I got it and I stripped the top trying to turn it with a properly fitting screw driver. I am taking it to the dealer Saturday to see if he can fix it or exchange my carb. It should be under warranty I hope.

On this site many people have stated that they are using between 120 and 132 for their main jet. But I also talked to Joe at Desert Toys today and he said that defeats the purpose of the 32MM carb. He has a customer with a Joyner 250 running a 160 main jet and they drilled out the pilot jet to make it bigger also.

So I am confused about why so such a range of opinions. I know with my Honda CRF450R usually the hot set ups become pretty apparant and the forum people usually all say the same things eventually.

I am not sure where to go, but I was hoping I could fix it myself without going to the dealer, its a long drive in a traffic prone area.

I am also wondering if all of you guys order your jets from dealers or are they common with anything else and available somewhere other than a buggy dealer. And can I or should I buy a whole jet kit somewhere?

I know this question is long so thanks for reading it.

Posts: 93

I was thinking the Joyner and the Hammerhead used the same engine, the CF Moto 172MM-C. I didn't realize the Joyner uses a different carb. That would explain the big difference in the jet sizes. If your carb uses round Keihin style jets you can get them from allot of places. I got a bunch of different sizes from Dennis Kirk. If you haven't already done it adjust your valves. It's really easy and it may save you from the headache I recently had.

Posts: 96

The Carb is KEIHIN 172MM according to the Manual

Good call on the valves. I will do that tomorrow. I should have thought of that right away. Hopefully its not too hard. I think the manual shows how to do it.

Z

Posts: 3980

have you checked the color of the spark plug to see if you are running lean or rich?

Posts: 96

The spark plug got dark within a just about 5 minutes of warm up, then I ran it up one time, parked it and pulled the plug.

I adjusted the valves and starts right up fine, but then runs like crap even during accell. So I think I made the valves. Worse. I will be trying it again. Seemed simple but intake valve was little wierd.

The intake valve initial placement was pretty far inward all ready. So I used the dowl in the spark plug hole method of finding top dead center. Actually the valves were easy to move in either stroke rotation I tried. But intake valve at one point would go all the way out and then when I moved back in and then tried to move it back out, it locked in position about where it was initially.

So I tried a few different times and it seemed to keep landing in the same spot so I moved it in one marker and tightened them down.

So that is where I am at. I would have posted ealier, but buggynews has not been loading. I am guessing server issues.

Z

Posts: 96

Man, I would never make a good mechanic as job. I would go insane with all the stuff that is supposed to work one way and doesnt.

I cant get the top dead center cap off. There must be ten different things on this joyner that you have break or ruin to get off. I love the buggy and the price. But I have several jap bikes and quads and I cant remember the last time I stripped or broke anything. I have good tools and took off that filter thats in the way so I have plenty of room and leverage with a larger craftsman screw driver. And it is stripping. Its not bad yet. I stopped before it got too bad.

That dang cap is welded into the head!!!!!!!!!!!!!! Anyone else or I am I the only idiot?

Posts: 93

Sorry that didn't go so well. Something is not right. With the piston at TDC on the compression stroke you should be able to turn the adjuster and feel when the rocker arm touches the valve. It's not a definite stop, just where you start to feel resistance. If you turn the motor by hand put your finger on the spark plug hole, when you feel air coming out stick the dowel in the hole and stop when the piston gets to the top. This is where you want to be. Always turn the motor in the direction it runs, counterclockwise looking at the variator, this will keep tension on the cam chain in the right direction. At this point if you can't feel any change when you move the adjusters you could have a broken valve spring. If you pull the carb off you can see the intake valve. It should move slightly when you move the adjuster. You should be able to see the valve hit the seat. If you can see this and can't feel it either your adjuster is too stiff or your spring pressure is too light. The problem could also be on the exhaust side.

Posts: 96

Yeah,

thats the technique I used. I saw you or someone else describe it on the Valve post. Any thoughts on the dark spark plug and my jetting?

Posts: 93

A dark plug means there's fuel going through the engine that isn't getting burned. This is usually from being too rich but it could also be low compression or weak ignition.

Posts: 96

Its running great now. I went back to the dealer today and I showed him what I was using. We tried the stock elbow with my large K&N, we tried no air filter and then we popped on this one.

http://www.knfilters.com/search/product.aspx?Prod=RU-1880

It ran like doo doo with anything but this air filter. And I am using a 137.5MM Jet. He said he tested a lot of different setups over the years and this one just works. Some how the air flow is better with this little one attached right to the carb than with any other setup.

So for you guys using smaller jets, this maybe something for you to try. The nice part is it fits easy and doesnt need a lot room.

I am tripping out on how magical this seems. Because I have never seen an airfilter have this dramatic of an effect. I have changed, modfied, and had many air filters fall off older (70's) model bikes in the past, and nothing has made this big of a difference.

Thank you guys for all of your help.

Scott