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Author Topic: Put a 38mm air stryker on, now it wont run at full throttle.  (Read 4522 times)

corvan

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Put a 38mm air stryker on, now it wont run at full throttle.
« on: May 12, 2008, 06:22:38 AM »
I changed carb only, if you use idle-3/4 throttle it is great, but past 3/4 and it will act very rich and foul plug if you stay in it, yes I inspected carb, all passages and jets are un plugged, the carb is new, so I believe it to be ok, my thinking is, can I be pulling the slide so far that it is allowing the main jet to flood the engine, should the needle not come all the way out of the nozzle? It runs geat and the plug is a little dark and wet, so I know I can lean it a little. Hoping someone has had this problem before and knows the fix. Bike is totally stock, just went to a 38 carb is the only mod, oh it does this with airbox lid on and off, but I ride with it on, double air inlet tubes done also. Jetting 180 main, 48 pilot. Thanks!
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1985 fl350, 2007 honda 450r, 2008 polaris RZR

Rich Paulson

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38 mm carb install
« Reply #1 on: January 18, 2009, 10:00:33 AM »
Just wondering if you were able to resolve your issue with the larger carb. I also have a 38 mm (Mikuni), but have a pipe and K&N air cleaner on my FL350. Just rebuild the motor entirely, and don't want to fry the piston.
Mine seems to start right up but no matter what I do to the jetting/airscrew, needle setting - it still falls on it's face. I have only had it out for a test and tune session since the rebuild. Seems like the ignition fails once I load it down from 1/2 throttle up. I have't even pulled the plug, probably instantly fouled from poor jetting/setup. I have also read the the larger carburator selection is not the best way to handle a stock or simi-stock machine like mine.
Any feedback from the group would be appreciated
Thanks
Rich Paulson
FL350
Works, K&N, 38mm carb, 5 gallon tank, watercooled cylinder head, banshee radiator, power bloc clutch
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hoodlum

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carb
« Reply #2 on: January 18, 2009, 10:59:09 AM »
What main jet size, and what needle setting are you running?
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Rich Paulson

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carb
« Reply #3 on: January 18, 2009, 12:50:46 PM »
I guess I didn't give all the info on my carb.
I put a power jet kit on this Mikuni flatslide 38mm.
The current main is a 280, the added power jet kit has a #80, the needle jet  is a 389 R-2, have the needle set in the middle groove. I temporarily pinched off the fuel line to the power jet kit to see if I was way too rich, warmed it up and reved it and it still was doing the same thing. I have disassembled and cleaned the carb out to ensure no blockages
This engine will not run as if the spark is going away completely. I just pulled the plug and it is suspect for being fouled as it is wet, oily and dark.
Maybe a fresh plug and try again?

The last motor burned a hole in the piston running just the original main jet system (no power jet) and was sized at a 330, needle set in the middle position. That carb set-up also had the same issued with the motor seeming like it lost the spark somewhere past mid throttle.
What do you think?
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Rich Paulson

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Put a 38mm air stryker on, now it wont run at full throttle
« Reply #4 on: January 18, 2009, 12:58:36 PM »
Your problem seems easier that what I am dealing with. It seems like you should go down one jet size at a time and do the plug check method for your main jet size. There is a blog at this site on how to jet your carb that will help. I'm no expert at this, though, since I can't seem to get the jetting correct for my ride. I would use the info at this site for sure as it is what I read in the Mikuni tuning guide.
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PilotHawK

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Put a 38mm air stryker on, now it wont run at full throttle.
« Reply #5 on: January 18, 2009, 05:53:36 PM »
Black, wet spark plug. Sounds like you are too rich! Look at this jetting guide! Remember to take notes about what you have in your carb when you have it apart, and what you've already tried.

http://www.yellowdogracing.com/techstuff.htm
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hoodlum

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Re: carb
« Reply #6 on: January 19, 2009, 05:01:58 AM »
Quote from: "Rich Paulson"
I guess I didn't give all the info on my carb.
I put a power jet kit on this Mikuni flatslide 38mm.
The current main is a 280, the added power jet kit has a #80, the needle jet  is a 389 R-2, have the needle set in the middle groove. I temporarily pinched off the fuel line to the power jet kit to see if I was way too rich, warmed it up and reved it and it still was doing the same thing. I have disassembled and cleaned the carb out to ensure no blockages
This engine will not run as if the spark is going away completely. I just pulled the plug and it is suspect for being fouled as it is wet, oily and dark.
Maybe a fresh plug and try again?

The last motor burned a hole in the piston running just the original main jet system (no power jet) and was sized at a 330, needle set in the middle position. That carb set-up also had the same issued with the motor seeming like it lost the spark somewhere past mid throttle.
What do you think?



Not too informed on the Mikuni's......
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Rich Paulson

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Put a 38mm air stryker on, now it wont run at full throttle.
« Reply #7 on: January 19, 2009, 08:11:58 PM »
Your right, I'm probably not as informed as I would want to be. However, I did look on the internet for the original jetting configuration for the TM 38 that I am running and will be setting it up to match the  original two stroke settings listed at the Sudco Mikuni site. The main jet listed is a 230. I had a #250 Main plus the #80 power jet originally. Probably just flooded the motor and fouled the plug as it reved up.
According to the instructions for the power jet kit, you take about 25% off the main jet size(230), which would make the main jet size  a #180 and the power jet a #60. The power jet kit is suppose to give fuel for mid range to WOT.
Here's the kit I am using.    
Power Jet Kit Universal MK-406

"""The TM Series bodies are designed to accept Power Jet Pump Kits. Power Jet Kits are ususally used on carburetors in 2 stroke engine applicatons to prevent leaning out during extended full-throttle running.

Fits 36-44mm

Includes #80, 100, & 120 power jets""""

There are instructions on how to jet any 2 stroke machine. I have learned that the  basic methods of tuning need to be applied to this application.

Time for some fresh plugs and patience, and I'll see what I can do with this carb. I"ll give up the results as soon as I can

By the way, what carb do you think will work the best for a FL350, with a pipe, K&N, V-Force reeds, watercooled cylinder head?
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PilotHawK

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Put a 38mm air stryker on, now it wont run at full throttle.
« Reply #8 on: January 20, 2009, 08:05:52 AM »
LOL, you're getting into the Ford VS Chevy debate with that kind of question. Some people like Mikuni, some like Keihin. The most important thing about carbs is that they meter the fuel correctly. The second thing in my book is familiarity with the carb you want to use. A carb that you already know something about is going to be much easier to tune than a brand new one. Jetting is not Voodoo. If you approach it in a scientific way you will eventually get it right. If you didn't like the jetting article I posted the firt time try this one.

http://www.eric-gorr.com/carb%20cleaning%20and%20jetting.pdf
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