Tecate Seized....oh man

[BigGreenMachine]

My T3 shut off the other day at my friends place because of a fouled plug, so I cleaned it and she fired again then shut off, same problem but now she wouldn't start. Brought it to me cousins garage and began to strip and clean the carb, reinstall my reed spacer and check all my wiring. I first noticed a buildup of unburnt gas and mix in my headpipe so I figured enough is enough and moved the clip on the needle up one position to lean the bike out so she wouldn't foul plugs and leave unburnt gas in the pipe. Put everything back together and fired it up, worked great, seemed like it had some nice power, no stumbling or hesitation, wicked. After 5 mins of riding i went for a nice run, W.O.T. up to 5th and then she locked...she isnt seized solid but I have zero compression...argh...

I left it at my cousins since our garage is full, poured some twostroke oil in my cylinder and called it a day...tomorrow after work I rebuild with my spare cylinder and rings.

Now when I do it I'm putting my needle clip back to center and hunting for jets. Its rich right now at 460 main and 40 pilot with the needle in the middle setting. The carb is a 38mm Mikuni TM off a Husky 250 MX bike. Where can I buy jets online? My local shop hasn't been much of a help.

All in all, fun day! :w00t:

[twgranger]

the same thing happened to me before, one day it was rich and the next day it blew. I didn't think the needle had anything to do with W.O.T? I must be wrong.

[83185s]

um wats w.o.t ?? anyway u could prolly get them from howdy on here or any atv place like www.denniskirk.com or
www.chaparral-racing.com or www.rockymountain.com

[Wickedfinger]

the same thing happened to me before, one day it was rich and the next day it blew. I didn't think the needle had anything to do with W.O.T? I must be wrong.It dosent - it effects carburation from about 1/4 to 3/4 throttle. While a million things might have happened here - I would venture to say the damage was done before his W.O.T run - which would make sense since the only thing he touched was his clip position (seems wierd that it happened so fast though). Since you have a completely different carb from a totally different application running on your Tecate - one which it really wasn't meant for - I would venture to say that when you get that thing back together, you need to do some serious carb tuning. Since you said you were stove piping and collecting unburned fuel in your pipe, I think you are WAY over jetted with your main and probably the pilot too (F.Y.I. - my 400L Scrammy with a 38mmTMX flatslider carb only runs a 280 (summer) - 290/300 (winter) main, a 25 pilot and a #58 needle - and the quad is well modded). You need to consider trying out a few different needles (length, thickness and tapers) and maybe slides as well.
Where can I buy jets online? My local shop hasn't been much of a help.It should just take the std. Micky big hex jets.

[tecatecrazy]

wow 460 main sounds huge. I'm running a tmx 38mm with a 260 or 280 main(cant remamber which). check the jimmy white manual for a starting place and jet from there. even though the carb they are using in that manual is 20 years old, the recommendations should give you a good starting point. good luck with your rebuild.

Joe

[BigGreenMachine]

So your saying it was on its way to seizing before I got to W.O.T.? The needle should be right out of the seat at W.O.T., so it should be getting all the fuel it needs at that point, especially with a 460 main. For jetting I'm thinking clip in stock postion with a 40 pilot and 390 or 400 main.

[Wickedfinger]

So your saying it was on its way to seizing before I got to W.O.T.? The needle should be right out of the seat at W.O.T., so it should be getting all the fuel it needs at that point, especially with a 460 main. For jetting I'm thinking clip in stock postion with a 40 pilot and 390 or 400 main.
No, what I'm saying is since you raised the clip position, you effected the needle by keeping it in the jet longer - which creates a leaner condition. You said you were just "riding" around for 5 minutes - riding to me means 1/4 to 3/4 throttle, which is right where you leaned your fuel delvery at. You probably were well on your way to a blowtorched piston for a long time before you even changed the clip and punched it WOT because of the carb not being tuned right. Personally, I think you have been running a needle thats way too long, with the wrong taper for what Kawasakis engineers designed the motor to run right with. What happened from there is a mystery - but - I think when you tear it apart, you will see the "siezed" part of it will come from a melted crown that has pushed your rings out and severly scratched the bore before the piston cooled down enough to shrink back down enough to move again inside the jug.

[BigGreenMachine]

Ok, Wickedfinger, John is it? Bare with me please. So your saying even if I set the needle back at the middle setting, that the same thing will eventually happen again?

I need a shorter and fatter or shorter and skinnier needle jet? I'll compare the needle in the 34mm stocker to the needle in my 38mm carb to get a base. Along with that a much smaller main and possibly a little smaller (say 35) pilot?

Anyone with a similar carb have theirs setup dead on?

[Wickedfinger]

Ok, Wickedfinger, John is it? Bare with me please. So your saying even if I set the needle back at the middle setting, that the same thing will eventually happen again?
Maybe ... you are going to need to trouble shoot it really. I just finished working up a carburation chart that may help you - I have been working on it off and on for a while, but your post finally made me finish it.

I need a shorter and fatter or shorter and skinnier needle jet?
Thicker needles are "leaner", higher taper numbers are "richer", longer needles create a leaner condition throughout the throttle. You have to, again remember that your carb came from a dirtbike motor and that being said, dirtbikes are "ridden" ALOT differently than ATV's - therefore their motors are tuned differently.

[BigGreenMachine]

This is actually what I've been going by. Your explanation of the needle answered my questions great though.

http://justkdx.dirtrider.net/carbtuning.html

[RacerRichie]

Dump that carb.

[NICKG]

you can get all the jets and parts from sudco. cheapest place around www.sudco.com
just so you know that if you run the thing really rich, you run the risk of seizure...the rings get gummed up and the excess fuel in the mixture washs the oiling off the clyinder walls. and it gets all foul down there, i recall using like 280 or smaller in those carbs and leaner with boyesen reeds. double check the crank bearings to you know those aren't bad now too

[TimSr]

This whole thread seems to be an awful lot of speculation, considering you havent taken the top end off and verified that the piston melted. It may be totally unrelated to carburetion. You may have broken a ring or cracked or broken a piston or something else. First you need to see if its actually melted, or if it failed for some other reason.

Here are a few other factors to consider.

1. Cold motors run very rich, the colder, the richer. Cold air makes your bike run leaner. What this means is that in cold weather climates, you can expect to foul lots of plugs during startup and warmup. The mistake I see people make so much is leaning carburetion to compensate for this. Then when the bike warms to operating temp, it is running way too lean. Carbs should only be adjusted based on untainted plug readings from a hot motor, and should never be adjusted based on smoke, oil in the exhaust, or how many plugs you foul during warmup. Also make sure your cooling system is working properly. Again, a hot motor burns lean, and I have melted a piston in one carbureted right, due to a cooling system failure.

2. When your top end is worn, i.e. rings, bore, etc, it will give all the symptoms of runnning rich. Compression, and top end condition should be known before doing any carb adjustments.

3. Your main jet controls fuel flow. Your needle only has the ability to limit it, when its partially plugging the main jet. When your throttle is open, the needle isnt doing anything because its no longer blocking flow. If you have the correct main jet, its exteremely unlikely that you were able to melt a piston by changing the clip position, and it has no effect when the throttle is wide open. .

[BigGreenMachine]

I haven't cracked it open yet, thats a job for Saturday, I'll take lots of pictures for you guys. Hopefully its not too bad but I'm expecting the worst. Tim its a brand new piston, rings and sleeve. I will surely follow your advice and after I move the clip back into the stock setting I will do a plug chop and see where I need to make adjustments.

I'm not dumping the carb, its a new one from eBay and I bought it specifically to use on this bike for a price that won't just let me not use it.

[Wickedfinger]

This whole thread seems to be an awful lot of speculation
thats precisely what it is ...... tear that thing apart and take some pics. Tim, you don't think a 460 main and a 40 pilot are way too much for a Tecate 250?.

[TimSr]

Im a big believer in maximizing and mastering the full potential of a stock motor, neither of which are done very often, so I have no experience with his specific carb. I run stock carbs. I cant even tell you what the stock size the stock Mikuni carb is on my TriZ, but I can say that mine has a 420 main, with the stock pilot, and I think stock main is like 470 or something, so it doesnt necessarily sound too big to me, but I would definately run some plug checks whcih will tell me pretty quick.

Big Green, the fact you have a new sleeve and piston makes it all the more suspicious. Sleeving is a very precision process, and there are a lot of hacks out there. I dont know who sleeved yours, and Im not saying they did a lousey job, Im just saying its suspicious. I just got off the phone today with PR Racing who rebuilt my crank, as I was checking to see if they could resleeve a TriZ. Incidentally the guy I talked to is a former Hi Performance TriZ builder, and had plenty of stories to talk about. Anyways, they used to do resleevng, but the actual labor involved in doing one right, about 5 hours, no longer makes it cost effective for them, and he was talking about all the hacks out there doing resleeving without finishing the job of doing all the portwork and matching that goes with it. He said they now send theirs to Wiseco, and recommended I do the same, which I did. I guess youll know when you open it up, but if its busted up and not melted, Id have some questions for whoever resleeved it.

[BigGreenMachine]

so when I order jets is it a good bet that the JWR manual jetting specs are a good place to start from? So far I've found the needle jet but not the needle, where can I find needles? I'm probably goin to have to call and order.

[3Razors]

Once you tear the motor down, by looking at the piston an expert motor builder can tell you what went wrong.

Go to www.carbparts.com for any carburetor parts. They have everything!

[BigGreenMachine]

Got this from a review.


The Mikuni TM38 carby showed up at the Trail Rider garages with stock brass and settings, noted as air screw 1.5 turns out; number 6AEJ3-64 needle with the needle clip in the #2 (second from top) position, a 40 pilot, and a stock 3.5 slide. Our bike came with a 430 main jet, while the owner's manual claims that a 450 main is stock. Right off the bat, running the bike in this state of tune with premium pump gas found things kind of lean on top, yielding a slight detonation when pushed.

[RideRed250R]

did u check the ring gaps and stuff be4 u rebuilt the top end? u could have also had to much of a gap and got play and KABOOOM. It could be trailprotrailpro sleeve, i dont think so but who knows.
adam

[BigGreenMachine]

Yupp, checked rings and gapped them correctly. The sleeve in both my cylinders was done by CT Racing in Cali and look to be top notch.

The review above was for a 96 Husky WXC 250, the bike I bought the carb from, mines a 94 model.

[3Razors]

The way a carbs jetting performs on one bike can be 100% different if you but it on another bike. There are so many variables such as pipe, ports, bore/stroke combos, intake size, intake, bike weight, ect., you can really mess your bike up unless you know what your doing. If your carb is the Mikuni TM38 flatslide carb recommended for the Tecate from the Jimmy White handbook then the jetting info is very good but it is still only in the ballpark. The jetting that was given by them was a formula for the KX250 cylinder, Bassani Pipe, and still using the airbox. Your jetting will be close with small differences if you are not using the same setup as the handbook.

[Mr. Sandman]

The way a carbs jetting performs on one bike can be 100% different if you but it on another bike. There are so many variables such as pipe, ports, bore/stroke combos, intake size, intake, bike weight, ect. Here's some addtional food for thought on jetting, since you really don't have enough to think about right now. Other things that can drastically affect how or which way you shuld jet your carb are, the altitude of your riding place, ambient air temperature, and even changing to a different premix oil. Good luck!

[BigGreenMachine]

Tecatecrazy, care to share your jetting specs with me? We have the same carb with bikes setup almost the same, only difference being your KX cylinder. I'd like to know your specs for the needle, needle jet and pilot jet. Anything else would be most helpful. Thanks

[tecatecrazy]

without looking: 280(might be a 260;cant remember) main 40 pilot and needle second position from top

Joe

[BigGreenMachine]

thanks Joe.

Tore the topend apart today on my Tecate. The rings are toast, almost melted into the piston in 3 spots. The cylinder has some light scratching, nothing major, a hone and new rings may handle it. I put my fresh piston, rings and cylinder on...gonna button it up a little later. Got some work left to do but its nothing major.

Before I run it again I'm gonna order jets and get that out of my mind.

[Curtis-Tecate3]

hey bigGreen. Did the same shop do both cylinders.? I would seriously check the ring endgap before putting it back together. Did the shop that did the cylinder have the piston & rings when they did the job?

Curtis.

[BigGreenMachine]

CT did both sleeves for me. They included two Wiseco pistons, rings, piston pins, circlips, and wrist bearings. We checked the endgap on the first set of rings and I checked the endgap on the rings I installed Saturday. My problem was jetting plain and simple. Besides, I had the topend off a day after I had ran it becuase she leaked coolant into the cylinder so I fixed that, checked the cylinder at the time and it was in perfect condition, if the rings had been gapped wrong there would have been scoring then at the time. Just so you all know I fixed the coolant problem with a new head gasket (which was the problem) and it hasnt leaked since and cooling has been fine.

[BigGreenMachine]

Ordering jets tomorrow, 270-310 main and a 35 pilot, going to raise the needle to one from the top. Before I ride hard I'll do some plug checks with the bike good and warmed up. No mistakes this time. Alot of my friends are like why arent you riding yet? Does it run? Its pissing me off and I got to ride this thing in front of them to quiet them down lol. Have to get my Spidertracs mounted and my seat covered too. The little things are what holds a project up.

[Wickedfinger]

.... take your time and do it right, thats all. Let'em wonder.

[Tecate250]

Old thread but do you have a pic of your piston? Mine sounds like it did the same thing but I dont know.