Triz mod carb

[tippmann]

I bough a 38 mm tm mikuni but its a real pain in the ass to set up the tm needle are all different of vm etc

So i read that keihin are better then mikuni and way easier to set up so im shopping for a pwk. Carb on ebay my z is ported dg pipe v force 185 psi compression wrench report recommand a 38 but i found a post ehere a guys prefer. A 39 mm and there is one on ebay that a 39 mm quadvent bored to 41 mm but its bid only price for now is 202 + 25 ahipping. And a brand new 39 mm pwk is 250 shipped ,, what should i choose ?And if its the bored carb what the max priceni should give for it ?

[zmpolaristech]

First question is, Are you still running a fuel pump or not? If you are, you need to find a pwk set-up for a fuel pump (smaller inlet needle, so the fuel pump can't overcome it). I buy used 39 pwks off of snowmobiles, for my Zs, since most all sleds use fuel pumps, they go right on. All you have to do is buy a choke assy, different jets and jet needle (52 pilot, cel needle, 165-170 main) I have purchased a few SETS off of late polaris xc600 & 700 sleds for DIRT cheap...less than $50 ea average!. If you are running a top mount tank, just about any dirt bike PWK will work, since they are set-up for gravity feed.

Example:
A fuel pump style pwk running off a gravity feed tank, will run the bowl dry on a good pull=lean and junk engine
A gravity feed style pwk running off a fuel pump, will eventually flood and puke fuel all over because the inlet needle can't stop the pressure of the pump.

Just keep this in mind while searching for a carb.

[tippmann]

Thx alot for this capital info is there any sled model i could get the air strikertech with the carb ? Or wich sled have 39 mm

[tippmann]

I dont find any but when you say it will flood because the inlet is too large withe fuel pump dont the extra fuel will simply return to tank via the return line ?

[badass350x]

I dont find any but when you say it will flood because the inlet is too large withe fuel pump dont the extra fuel will simply return to tank via the return line ?

Yes thats Exactly how it works!!

[tippmann]

So that do nothing if my carb inlet is for gravity

Example:
A fuel pump style pwk running off a gravity feed tank, will run the bowl dry on a good pull=lean and junk engine
A gravity feed style pwk running off a fuel pump, will eventually flood and puke fuel all over because the inlet needle can't stop the pressure of the pump.

Just keep this in mind while searching for a carb.

[badass350x]

Buy the carb you want, run the fuel lines like factory = running!!! That T is there for a reason To take the pressure off the needle and seat!!!!!

[TimSr]

With your setup, basically the same as mine, I think you're having so much trouble setting the carb up because its way too big. I haven't worked with the carb you have, or the pwk39, but the stock carb is 32mm, and using the same style of round slide Mikuni as stock, (which doesnt require intake change) I got very good results with a 34mm round slide Mikuni, but when I used a 36mm it was pain to setup, ran great n top end, but always ran rich everywhere else after several needle/needle jet changes, lost a lot of low end power, and was never very stable and was horrible in cold weather. I think most of the people using Keihen are using the stock 250R one, which I think is 34 or 36? The point is, I think the only thing to be gained by putting anything larger than a 36 with your setup - ported cylinder w/ DG pipe, is lots of headaches. I'm back to stock carb on my MX TriZ, and nobody is leaving me behind in the straightways and the 34mm Mikuni round on my trail machine.

Buy the carb you want, run the fuel lines like factory = running!!! That T is there for a reason To take the pressure off the needle and seat!!!!!

I agree completely! There is nothing to be gained by eliminating it.


Did you ever find what was causing your coolant leak?

[zmpolaristech]

Buy the carb you want, run the fuel lines like factory = running!!! That T is there for a reason To take the pressure off the needle and seat!!!!!

The T only relieves SOME pressure...believe me, their is still a ton of pressure in that line when running, enough to overcome a large inlet needled carb.

[tippmann]

Its ok aboutthe leaking notsure about thereal origin of the problem

[El Camexican]

First question is, Are you still running a fuel pump or not? If you are, you need to find a pwk set-up for a fuel pump (smaller inlet needle, so the fuel pump can't overcome it). I buy used 39 pwks off of snowmobiles, for my Zs, since most all sleds use fuel pumps, they go right on. All you have to do is buy a choke assy, different jets and jet needle (52 pilot, cel needle, 165-170 main) I have purchased a few SETS off of late polaris xc600 & 700 sleds for DIRT cheap...less than $50 ea average!. If you are running a top mount tank, just about any dirt bike PWK will work, since they are set-up for gravity feed.

Example:
A fuel pump style pwk running off a gravity feed tank, will run the bowl dry on a good pull=lean and junk engine
A gravity feed style pwk running off a fuel pump, will eventually flood and puke fuel all over because the inlet needle can't stop the pressure of the pump.

Just keep this in mind while searching for a carb.

Very interesting. I posted this a few weeks back http://www.3wheelerworld.com/showthr...I-Z-Fuel-Pumps
What you are saying fits my problem bang on, yet at the same time what others here are saying about the tee allowing the excess fuel bleed off makes sense too. However (no offence to those who disagree with zmpolartech) given that I can't seem to stop my overflow problem I'm going to have to agree with your comment as seeing is believing and I suspect the uphill push required to return the excess fuel to the tank may be more than is required to push the needle off the seat, even though the hose is larger. So my plea for advice is as follows: I’m running a 38mm PJ which has the intermittent overflow problem (as well as an idle issue) so I’ve ordered a new 38mm Air Striker to replace it. So, this “inlet needle” you are talking about, is it something that can be bought and added to the carb I ordered, or is it cast into the carb body? I seem to recall the PJ seat is part of the body and looking at drawings of the Air Striker I don’t see a removable seat like the Mikunis have. I’m also thinking that if I can’t make the change then perhaps I can run a longer fuel line to the carb and route it so that it offers a little more resistance, or put a valve in it to restrict flow. Any thoughts? Also if anyone is running a standard 38mm Air Striker from a dirt bike and a fuel pump with or without problems please chime in. I’m going to try calling Sudco today to see if they can tell me something about the inlet sizes.

[badass350x]

Im running 38's on two of my z's and they run perfect, one of the Im running a brass T with a bigger return outlet which will allow more fuel to return to the tank! The for other one is factory T with no problems ..

[zmpolaristech]

inlet seats are pressed in to the keihin carbs and are non replaceable. I know that some people have had some success running the large inlet needled carbs, but it WILL eventually cause a problem (when running the stock-T or one of ronnies billet Ts). A large brass t with equal size nipples all around, should solve the problem (the way badass350x is running them). But what I am telling you is true...I have seen first hand what CAN cause some severe headaches.

[El Camexican]

But what I am telling you is true...I have seen first hand what CAN cause some severe headaches.

Yep, I'd rate massive dead patches of lawn and running out of fuel after 30 minutes of riding in the headache catagory. Thanks!

[tippmann]

Loll ok goodto know !