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View Full Version : carbs - 39mm or air stryker?



Westro
08-31-2004, 12:34 PM
Folks I need some help.

I am coming from a Banshee and have had my R for a year. So, my R when I bought it had (has) a 39mm carb on it. I am thinking that it is a little large.

So, would a 38mm air stryker help me out? Seems like the bike doesn't have decent mid range and stumbles on it's self. But with a clutch slip I can get it up in the RPM's and keep it on the pipe.

I guess I haven't ridden a properly jetted/tuned R and am looking for some advice on 38mm vs 39mm carbs.

I also might be having trouble with the reeds. The previous owner said it was eating reeds. There is a V force block in there with carbon fiber reeds. Is there a difference between the CR blocks and the R blocks? And how can you tell. I think I remeber the dumb *** telling me that he put a CR block in the R I bought. But there is no identification numbers on the V force to look up and see.

Well thanks, I am new to the R world. Lots of seat time on the twin two strokes and CR dirt bikes.

:devil:

310Rduner
08-31-2004, 05:19 PM
If it is a cr cage then it is definately to blame for the reed snapping problem. Get rid of the cr cage and pick one up for the R. As far as carbs the 39mm will definately flow more on the top end, but you will lose a little bit of the bottom end because it has a lower velocity. Depending on the purpose of the bike ie: woods -low mid, or general midrange you will want to go with different carb and porting. For woods riding I would look at stock 34mm, and 35mm carbs. For all around a 38mm probably wouldn't be too much if your motor is reasonably built. I wouldn't go to 39 unless you plan on extensive porting, and a higher powerband.

velocityatv
08-31-2004, 05:58 PM
Sounds like you guys are heading the right direction. I agree get ride of cr cage and get the one for the R. I would go with the 38mm A/S and v-force reeds. You probly will get rid of a lot of the stumble by putting in the right reeds. What pipe do you have, and has the cyl been ported? Upping the compression might help a little too and its a cheap hp gain. I run a RPM adjustable counterbalance carrier, it helps a lot when tunning. I'm running close to the same set up as you are and have enough bottom end to do anything and plenty of top end to hold my own against some of the bigger boys I don't think youd be disapointed.
:D

Westro
09-01-2004, 06:30 AM
I am running sparks pipe.

I think that I am going to replace the block and reeds. The V force that came on the bike has issues. And the stock one that I have in there right now just doesn't seem right.

Thanks everyone. I am thinking that reeds maybe all I need, because the 39mm should scream. I am looking for that hit that I lost when I went from my Banshee. The biggest thing is the R handles great, just looking to get her running good then start increasing the HP.

Westro
09-07-2004, 07:39 PM
I have a question...

My Vforce reed block, I don't know if it is for a CR250 or a TRX. But the stamping on the intake side (carb side) says DM 05.


Any idea if this is for a CR or a TRX?

Thanks

racerx573
09-08-2004, 12:06 AM
36mm Airstryker is perfect for woods type riding. Stock bore to 265...

38 A/S, is the norm for MX, and stuff like that.

39mm Is fine for MX, but I recommend a reed spacer, and an MX/midrange pipe to even out the power band.

I have run both a 38 A/S and a 39mm on each of my engines, and the 39 seemed to work best on wide open tracks, and the 38 was just good all around, but the 39 still worked fine on the rest of the tracks. I was running a v-force with a 1/4" spacer, and a Sparks MX pipe, on a 265cc engine.

Westro
09-28-2004, 12:24 PM
I replaced the reed block with the correct TRX reed block and the motor still is stumbling in the mid range. Still runs out well on the top end but the mid is lacking/bogging. I wonder if a needle adjustment would help me out?

Funny thing is that it seems worse when it gets warmed up good.

I was thinking about going to a 36mm A/S, how much am I going to loose? I wouldn't mind making the power more in the mid range since this bike is not a MXer anymore.

Bart
09-28-2004, 02:14 PM
Prices for new carbs:

http://www.pro-flo.com/proflo_keihin_flat_slide_carbs.htm#PWK%20SERIES

You may also want to see if C&D Racing can get you a better deal.

Or you can try ebay/classifieds.

wilkin250r
09-29-2004, 03:30 PM
If it's stumbling through the midrange, it sounds like a carb adjustment is in order. The adjustments are simple, if you have experience and know the different symptoms and remedies. You can play around with it and try to figure this out yourself, but you may get frustrated, may go backwards, or you may make the problem better, but not necessarily fixed properly.

Most race shops with a dyno have lots of experience with 2-strokes and the 250r in particular. Usually for about a hundred bucks, you get an hour on the dyno and a technician to help you, and you can get that baby tuned to perfection.

Westro
10-11-2004, 11:00 AM
Update,

I spent some time this weekend and got the 39mm dialed in along with new reeds and block.

Running really strong now, do I dare say that the power is on tap with my piped Banshee!

Thanks everyone, happy to be back on an R.

-Marc