Tecate carb advice

[vroomy]

Hey I'm looking to put a more modern carb on my 87 Tecate, been recommended a Mikuni TMX 38mm but will I lose bottom end with that size? My motor is stock with a k&n pod filter and DG pipe.

[nstyle73]

Somewhat depends on how you want to ride it as to what size carb you want. I have a 36mm on a 295 bike that is mostly woods ridden and a 39mm on a 295 bike that is usually ridden in more open areas. But both are ported accordingly and I feel that the 36 is enough carb for the woods bike. If yours is not ported, a 38mm will be a lot of carb in my opinion. My only experience with a 38 on a stock bike, the bike did feel sluggish on the bottom end. I had the jug ported by Flo-Tel for mid-top and the bike felt completely different with the same carb (obviously) and was still weak on the bottom end. Take that for what its worth.

[tecat-z]

Yes. 34-36mm for mostly stock engine. I happen to prefer the
Keihn PWK series carbs. Easy tune and an immediate upgrade
over old oem round slide. A 36 allows for plenty of performance to
be pulled out if the temptation occurs. Tremendous power can be
made on medium sized mixers, while retaining low throttle
crispness.

[barnett468]

Yup, 36 is ideal.

You can also increase your compression a little if you run 98 octane which will increase power and throttle response everywhere by a little.

[vroomy]

So 38 will definitely be too big?

[christph]

I wouldn't say a 38 is definitely too big. I run one on my 87 Tecate and it runs great. It just depends where you want your power. If you spend most of your time in low to mid range, go with the 36. If you want more top end, go with the 38. The TMX is a flat side carb is narrower in width and generally recommended for top end engines. If you want a low to mid range carb, I think a Keihin PWK or Mikuni round slide would be better.

[vroomy]

Ok the problem I have is I've bought a billet intake from Greg at Offroad innovation and its spaced the carb back a good 1/2" so now the k&n pod filter rubs on the shock. He did a bit of research and found the TMX carb is slightly shorter so will have clearance for filter, but the 35mm TMX will be too loose fit in the intake so the only option so far seems the 38mm however I love the way the bike runs at the moment and would hate to spend the money and loose bottom to mid power. Only other option is to see if the stock air box will fit but being the carb is pushed further back that might also be an issue? And I do prefer it without that big ugly box. Anyone got any other ideas?

[just ben]

Change the rubber flange on the intake if you want to run the smaller carb.

[vroomy]

Where can I get one from?

[just ben]

Parts unlimited,Dennis Kirk and several other places.

[MTS]

Sudco sells them there mikuni boots if it's a sprock intake, beware off the off brand intake boots there much larger and will not fit the billit intake properly. Or run a 38-39mm pwk....properly tuned it will rock your socks off!

[onformula1]

You could always buy a 38mm they sleeve it to 36mm for more low end, then if you end up with more mods you have it covered.

Here is a PWK that I had it was a 38mm bored to 40mm with inserts so I had a 40mm, 39mm, 38mm, 37mm and a 36mm carb all in one.

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[fieldy]

You could always buy a 38mm they sleeve it to 36mm for more low end, then if you end up with more mods you have it covered.

Here is a PWK that I had it was a 38mm bored to 40mm with inserts so I had a 40mm, 39mm, 38mm, 37mm and a 36mm carb all in one.

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ONFORMULA1-Is this the way they sell them( like a special order ) or is this an after purchase alteration thing. This sounds really great! Never heard anyone mention it before. Would you have to buy new needles or anything besides jets for each mm? Could you further explain?

[vroomy]

Yeah very interested where to get these sleeves

[onformula1]

ONFORMULA1-Is this the way they sell them( like a special order ) or is this an after purchase alteration thing. This sounds really great! Never heard anyone mention it before. Would you have to buy new needles or anything besides jets for each mm? Could you further explain?

Funny thing is- I posted pictures and info about these mods a couple of years ago and nobody cared? Now my computer and phone are blowing up...Must be timing?

I don't think you can buy them anywhere, I had the first set made, then made my own when I bought a lathe.

Keep in mind I "Borrowed" the idea from the Team Kawasaki Factory MX Works team many years ago.

They used them because it's a bunch of carbs in one and if you have a POD filter or a flexible air boot you just loosen the intake manifold clamp, push the carb back and out, swap it out put carb back in and tighten the clamp. 5 mins. tops!

On a smaller Supercross track like Bercy, France they would use a 36mm on a track like Mammoth Mountain MX they would use the 39mm insert or no insert. (40mm)

In most cases if the jetting is "Matched" from top to bottom you can change by 1mm with no changes with a 2mm change sometimes the main jet needs to be changed by one size, from say 40mm to 36mm it will need a main jet change and needle clip change.

If you have "Matched" jetting and good settings you will not need to change the needle, air screw or idle. (I always run zero idle)

The other neat thing is the modified carb with the 38mm insert will out perform a standard 38mm carb because of the taper on the insert increases velocity and gives the motor more snap off idle/bottom end.

I also have all the jetting settings for a PWK and PJ carbs.

I wonder if I can get my machinist buddy to CNC some for me....Hint, hint.

[onformula1]

There are also air horn mods, slide mods and tee vent mods that compliment the sleeves

[vroomy]

Can they be done also for the Mikuni tmx? Because that will be the carb I'll have to use

[cr480r]

Don't be scared to give the 38 a try. Your riding style has more to do with it than anything. A stock tecate engine is nothing like a stock Yamaha or Honda. '86 uses a full on KX250 cylinder right out of the box. The KX dirt bike of the same year came with a 40mm... And the later 250 bikes came with a 38 or 39 PWK depending on year...

[onformula1]

Can they be done also for the Mikuni tmx? Because that will be the carb I'll have to use

Yes, but I can't give you the proper jetting specs, just advice. (I am a Keihin or Dellorto guy)

[fieldy]

Well, thanks, this sounds like the Kat's meow. A good kit could be available with the knowledge and experience to back it up, hint, hint,...hmmm. I for one hope we hear more about this topic.
There is an article about hopping up the 86 KXT in the article section of 3WW. In the article they were running a 41mm and a KX 250 head gasket on a stock bore Tecate with a Bassani exhaust. Thinking that would have required or require a lot of experience jetting as the bikes were raced across the country. Sounded like the 41mm made it into an absolute rocket ship and the man got the hole shot at his first national on it that way. FWIR

[vroomy]

Don't be scared to give the 38 a try. Your riding style has more to do with it than anything. A stock tecate engine is nothing like a stock Yamaha or Honda. '86 uses a full on KX250 cylinder right out of the box. The KX dirt bike of the same year came with a 40mm... And the later 250 bikes came with a 38 or 39 PWK depending on year...

Interesting info. My concern is its gonna cost a bomb with the Australian dollar being so low, and the fact I love the response it has through low and midrange it worries me losing that after spending the $$$. I put a 36mm on my last 86 atc250r and sure it gave it more top end was horrible through the bottom end

[fieldy]

I've got a TMX on a bored RM 250 which an above poster claimed it was for higher reving engines. I wonder how much a torque spacer would help your TMX out Vroomy? Even how much it would help out the PWK's of a larger mm? Say a 38mm with a torque spacer?

[vroomy]

I have a billet intake which already pushes the carb back a fair way which is why I'm stuck using the TMX because it's pretty much the shortest length carb and allows enough room for the air filter

[fieldy]

Could you buy a uni-filter? They are more forgiving than a K&N. Uni-filters come in different lenghts. The KX 500 intake boot when used on a KXT is angled out of the KXT frame if you didn't know it. They are for larger mm carbs though. Same problem..... I only have some stock intakes and probably will get a KX 500 intake when I am not running an air box. I was going to look at those billet intakes you bought. I called in "14" about them but they weren't ready. There has to be a Uni-filter that would work? Maybe not....
My stock intakes looked horrible but they are not leaking and I put black RTV on the outside of them and they look good now. Hope I am not mentioning things you already know and I am learning a lot, thanks and good luck.

[onformula1]

I have a billet intake which already pushes the carb back a fair way which is why I'm stuck using the TMX because it's pretty much the shortest length carb and allows enough room for the air filter

You may want to consider the Keihin 38mm PWM, it is very short. On the left, PWK in the middle.


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[nd4speed]

There are Uni Pod and Twin Air filters that are angled.

Post # 283
http://www.3wheelerworld.com/showthread.php/94809-Kxt250-Tecate-3-What-Parts-Fit-Swap-Interchange/page19

And yes the 86 KX250 came with 40mm Mikuni VM. I have run the 40mm KX stock, 38mm TM, and 38mm PWK & Airstyker with Pods and no issues.

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