What size carb to use?

[talon67]

OK....I had a 86 250R Engine from FTZ performance with the long rod kit, spacer plate, paul turner pipe, boyesen reeds, air box eliminator, etc. It had a lot of porting done and was bored 120 over along with the stroker. I bought a stock cylinder, head and piston and returned everything to stock on the motor. I'll still be running the air box elim, pipe, reeds. I don't know whet to do about the carb. It has a 38mm mikuni flat slide that has been bored to a 40.5mm. This was used with the stroker motor. Should I get rid of this and get a smaller one? If so, which one? is this one usable with the stock bore and stroke? This is just used for trail riding. Thanks for the help!

[8686]

Since you mainly use your quad for trail riding and you returned your engine back to bone stock I would put the stock Keihin 34 PJ carb back on it. You'll gain a lot of low end power back compared to that big carb. Plus they can be bought used fairly cheap.

[IcutMetl]

Perhaps a 35PWK Air Stryker would be a good choice since you're running a modded airbox, pipe, reeds, etc.

What do the rest of you guys think?

[talon67]

Not that it should matter much, but it also has the CR250 electronic ignition......and a K&N filter

[86 Quad R]

Originally posted by IcutMetl
Perhaps a 35PWK Air Stryker would be a good choice since you're running a modded airbox, pipe, reeds, etc.

What do the rest of you guys think?


agree's X's 2

[79vwrabbit]

38mm Keihin PWK AS hands down. Get a CEJ needle-it is THE NEEDLE for the Honda 250R.

Service Honda sells a brand new one for a 2000 CR250R for about $170 if I remember. Make sure to get the larger boot clamp for the CR too otherwise the big carb won't fit!

The 35 PWK is an upgrade for sure, but the motor will still be a bit under-carbureted. Think: more air in an out=more power output. But a small carb chokes off the air supply, even for stock motors, in my experience. I know some woods riders (low-end power loving) that run bigger carbs.

The PJ is a "Piece of Junk" compard to any PWK Air Stryker. It's very difficult to jet correctly and the 34mm is just too small for a single-cylinder 250cc machine. There are good reasons why they're so cheap. I had problem after problem with the PJs on me and my brothers' quads. They just aren't well designed carburetors. Seemed to have a lot of problems fouling plugs too with the PJs (didn't foul a plug the rest of the season after I bought a PWK).

The 40.5 is a tad too big for a stock motor. The 39mm and up are better suited for big-bores and drag/hill climbers. The 38mm PWK AS is the best all-around carburetor. My brother runs the 38 on his completely stock motor with an aftermarket pipe and No-Toil filter. We like to ride the trails too, and man, does that thing RUUUUUNNNN!!!

[talon67]

I do like the PWK carbs. I had a PWK28 on my son's Blaster and it worked great. I think it came from Sudco racing? So I guess it's between the 35 and the 38? If it helps any....I like the low end more than the top end.... I run the woods trails some....but run in some open fields and fire roads as well. Any more advice on which one to go with? Also, where is the best place to get them? Is the 'service Honda' a website? Thanks again for all the help! I appreciate it! Dave

[79vwrabbit]

http://servicehonda.com/

It's a pretty popular site for OEM parts-discounted parts usually too. My local dealer is always more expensive than Service Honda. I've spent several hundred dollars in parts there (and saved several hundred too.) Their shipping charge is usually $9.00

Their catalog system isn't the most user-friendly. I usually just get a Honda part number and punch it in where it says Already Have a Part Number on the homepage.

When I first ported my OEM cylinder and was running one of those crappy Cool-Heads with the stock head gasket, I was fouling plugs right and left. I think my porting upset that old carb. I bet I had two dozen fried plugs on the bench and hours of frustrated carb tuning before I bought the PWK AS. Holy crap, it felt like my power HAD doubled! It actually idled like it was supposed to, and I didn't foul a single spark plug for the next 15 hours of riding (rest of the season).

In order to convince my brother to go with the 38 PWK AS to cure his plug-fouling issues at the time, I installed my own 38 on his stock 250R while my quad was out of commission for a week. Coming from the 34 PJ, he said it felt like it doubled his power from bottom to top, and he's a big fan of low-end power too. He was tearing around the farm grinning like a oppossum eating doo-doo in the moonlight ;)

The stock cable will work with the 38 if you very carefully trim off the metal clamp on the end (I used porting tools). But I think Motion Pro sells a special cable for it too. And the bigger carb is a little harder to fit into a stock reed boot. But we use the Boyesen RAD valve for the TRX, and Boyesen makes a boot that will fit the 38 perfectly to that cage. As for the airbox boot, it was discontinued from Honda a few months ago, so it requires heating in boiling water to squeeze it over that big ol' carb.

Hope that helps.

[1promodfan]

Originally posted by 79vwrabbit
38mm Keihin PWK AS hands down. Get a CEJ needle-it is THE NEEDLE for the Honda 250R.

The PJ is a "Piece of Junk" compard to any PWK Air Stryker. It's very difficult to jet correctly and the 34mm is just too small for a single-cylinder 250cc machine. There are good reasons why they're so cheap. I had problem after problem with the PJs on me and my brothers' quads. They just aren't well designed carburetors. Seemed to have a lot of problems fouling plugs too with the PJs (didn't foul a plug the rest of the season after I bought a PWK).



Not to hi-jack the thread, or cause any "rukus"....but a PJ carb is not as bad as you say. It depends on what kind of riding/racing you are doing. I personally run a PWK.......but its because of my riding style. I know of someone that runs a 38 PJ, and is winning races with it. Just my 2cents...........

[79vwrabbit]

Originally posted by 1promodfan
I know of someone that runs a 38 PJ, and is winning races with it. Just my 2cents...........

Hey, no problem-winning races must mean something is right!

But since Keihin runs the idle circuit through the choke one on the PJ models, getting them to idle well (a nice, racy idle) is the real trick...and not worth the trouble in my experience...

The PWK makes my day!

[1promodfan]

Originally posted by 79vwrabbit
Hey, no problem-winning races must mean something is right!

But since Keihin runs the idle circuit through the choke one on the PJ models, getting them to idle well (a nice, racy idle) is the real trick...and not worth the trouble in my experience...

The PWK makes my day!

That makes two of us.......PWK for me too. Everyone says the 38 airstryker is the one to get.

[IcutMetl]

That's what I hear too...I don't have anything else to compare my 38pj to; it seems to run just fine, but getting a consistent idle is a pain in the tail. 38PWK Air Stryker for me when the right deal comes along.

[Saul76]

I run a 36mm PJ on my 300R Aircooled engine. Idles great, terrific bottom and mid ... I didn't have any trouble jetting it.

Maybe on my watercooled TRX engine I'll feel different - but that's what came with the TRX I have so I'll be sure to at least try it and see where I get with it once I put the engine back together.

[talon67]

Originally posted by 79vwrabbit
38mm Keihin PWK AS hands down. Get a CEJ needle-it is THE NEEDLE for the Honda 250R.

Service Honda sells a brand new one for a 2000 CR250R for about $170 if I remember. Make sure to get the larger boot clamp for the CR too otherwise the big carb won't fit!

The 35 PWK is an upgrade for sure, but the motor will still be a bit under-carbureted. Think: more air in an out=more power output. But a small carb chokes off the air supply, even for stock motors, in my experience. I know some woods riders (low-end power loving) that run bigger carbs.

The PJ is a "Piece of Junk" compard to any PWK Air Stryker. It's very difficult to jet correctly and the 34mm is just too small for a single-cylinder 250cc machine. There are good reasons why they're so cheap. I had problem after problem with the PJs on me and my brothers' quads. They just aren't well designed carburetors. Seemed to have a lot of problems fouling plugs too with the PJs (didn't foul a plug the rest of the season after I bought a PWK).

The 40.5 is a tad too big for a stock motor. The 39mm and up are better suited for big-bores and drag/hill climbers. The 38mm PWK AS is the best all-around carburetor. My brother runs the 38 on his completely stock motor with an aftermarket pipe and No-Toil filter. We like to ride the trails too, and man, does that thing RUUUUUNNNN!!!

OK, so that's the best place to buy one? Do they have the needle also? Thanks!

[79vwrabbit]

Don't know if Service Honda can get a needle. I've gotten my carb jets and needles from Carb Parts Warehouse in Ohio.

http://www.carbparts.com/

I think I had to call them the past few times because they don't have an online ordering system set up yet.

Oh, I don't know if I mentioned, but make sure to get the bigger (70mm) airbox tube clamp for the bigger carb. It was made for the CR bike, and it fits the 250R boot nicely with the bigger carb. Trying to squeeze a smaller clamp on there, or a fat, generic one from Autozone just doesn't work out like the Honda part!

Can't go wrong with the Air Stryker and CEJ needle. People a lot smarter than me have concluded that the CEJ is THE NEEDLE for the 250R, and it has been tested in up to 350cc machines. It works very well on my little old 258cc beast. It's just lean enough to give great bottom end power and a strong midrange until the main jet kicks in!

[talon67]

Thanks! I imagine the boot on the front and the boot going to the filter (no airbox) should probably be big enough? It had the 39mm Mikuni bored to 40.5mm on it. Thanks again to everyone for the input! Thanks, Dave