Tecate KX250 hop-up question?

[rpjense1]

Hi guys! I've got a '85 Tecate that was running sweet up until last fall when the head gasket sprung a leak. Anti-Freeze then spilled into the cylinder and preceeded to score the cylinder & piston. Since the cost of a new sleeve or re-Nikasil cylinder was about $200, I decided maybe it was time to try the long awaited hop-up I've been meaning to try; The KX250 cylinder "bolt-on". Well, I found a decent KX250 cylinder (already sleeved) on eBay and had it rebored with new Wiseco piston. I also had the cylinder head and base slightly cleaned up to make sure everything seals up ok. Well, I put it all back together and tried firing that baby up. Nothing. I get the occassional 1 second rumble then she quits. My question is, has anyone tried this modification? From what I remember, it was recommended by Kawasaki in the Jimmy White Replica specifications. But if anyone has tried this mod or is familiar with it, do I need to do anything else? Different timing specs? I do get the occassional backfire. Jetting? I used the stock Tecate head gasket. And yes, I have spark, fuel and (plenty) of compression. Any ideas??

[wizzard]

how long did the bike sit up?

[rpjense1]

I assume you are referring to when it was last running. Last fall. But I've tried priming it and that doesn't help. Something seems way off. I tried surfing the web trying to get the KX250 timing specs for '85 and I can't find it. Has anyone done this mod or can refer me to an article that has?

[BigGreenMachine]

Well you bored the cylinder so arent you supposed to rejet because the engine needs more fuel/air to run the larger bore and compression...anyone care to add to this or tell me I'm wrong? The backfire would have me think your flooding.

[ange]

The KX cylinder breathes differently than the KXT one. The JWR manual doesn't specify how to set it up w/ the stock carb, because they recommend you getting a bigger 38mm flat slide...

Sounds like too much fuel getting in. Take the exspansion chamber off and see if you have fuel sitting in the exhaust system... then you know if you need to lean it out some more w/ different needle settings or jetting changes.

[200x Basket]

that was my cylinder!!! it should be the same. make sure dirt dobbers have not clogged your pipe. that was my problem, lol. then get someone to pull start you. if you have fuel built up in the bottom of your engine it will never start with the kicker.

[wizzard]

"I get the occassional 1 second rumble then she quits."
what you've described here sounds like something I had happen to a 250 R I had after I let it sit up for a while. Clean your carb out, specifically your jets. A can of degreaser, cotact cleaner or even WD40 should work. Put the straw (that comes with the can) in every port in the carb, spay, and make sure the spray is coming out somewhere else. This is the simplest way to clean your carb. Chances are your pilot jet is clogged and that's your whole problem. Take it out and try to look through it, if you can't see through it.....

[rpjense1]

The KX cylinder breathes differently than the KXT one. The JWR manual doesn't specify how to set it up w/ the stock carb, because they recommend you getting a bigger 38mm flat slide...

Sounds like too much fuel getting in. Take the exspansion chamber off and see if you have fuel sitting in the exhaust system... then you know if you need to lean it out some more w/ different needle settings or jetting changes.
Other than the 38mm flat side, do they recommend any other mods? They don't mention anything about advancing/retarding the ignition timing versus stock? Other than the carb, any other mods they recommmend? Where can I find a JWR manual? Anyone know if there's one posted online or the basic configuration (jet sizes, ignition timing, head gasket (kx-kxt), pipe, etc)? If Kawasaki has done most of the research, I'd like to piggyback on their R&D. Thanks!!

[rpjense1]

that was my cylinder!!! it should be the same. make sure dirt dobbers have not clogged your pipe. that was my problem, lol. then get someone to pull start you. if you have fuel built up in the bottom of your engine it will never start with the kicker.
200X Basket -- The cylinder has K&K scribed in it. What the heck is that all about? Did you sell it on eBay to rpjense? You ran this cylinder on an otherwise stock Tecate (carb, pipe, etc)??

[ange]

They give jet size and set up hints for the 38mm flat slide only.

No timing information is given.

Ebay is your best bet at finding a JWR manual. (none that I know of are scaned and online)

I recently had a similar problem, it would fire maybe once, then thats it. It was just flooded out really badly. A bunch of gas in the pipe, and the bottom of the engine.

Took the pipe off, got the fuel out, spun the engine a bunch to crank some of the gas out of the engine, drained the carb, then it started right back up.

Start w/ the obvious. Is there spark? is the plug wet when you pull it out?

[TeCaTe_MaN]

i knew a guy that actually pulled that off...man that was a beast...you need a KX500 carbuerator to make it work good...

[rpjense1]

I just had it out at my brother-in-laws and we were bump starting it using his golf cart as a mule. She would run for 3-4 seconds and then die off. My bro-in-law is a big 2 stroke roadrace (tz Yamaha) gearhead. He said something about the engine being one large pump, and now that it's flowing better (less restrictive), it needs less fuel. Needless to say, I'd hate to spend the rest of Summer farting around with my jetting, slides, needles, etc. So I think I'm going to yank off the KX top end, get my old cylinder resleeved and go back to stock. After spending a total of $300 on the cylinder. bore job, cylinder resurfacing (head & base gasket), beadblasting and wiseco piston/rings, I'm going to cut my losses now. Stick it out on eBay and see what happens. 20 years ago, an Enduro racing buddy of mine always used to say; "Bob, when are you ever going to learn? Stock is best". I think it's finally starting to sink in!! Thanks Guys!!

[deathman53]

I wouldn't do that, I'm sure its something stupid. they used the kx igntion in the jwr manual, I've heard of sometimes bikes not running because of too small of a carb. I had a 36mm on my tecate, What carb do you have?

[cliff2302]

how much do you want for the kit?

[rpjense1]

I wouldn't do that, I'm sure its something stupid. they used the kx igntion in the jwr manual, I've heard of sometimes bikes not running because of too small of a carb. I had a 36mm on my tecate, What carb do you have?
It's the stock 34mm. I'm curious about using the KX ignition. Did they recommend the KX ignition because of the lighter flywheel? Or is the timing different?? 38mm flat slide = $200 (plus jets, slide, needle), KX ignition & flywheel = $250. Ouch! This experiment is getting spendy. If someone wants to make me an offer, we should do it outside of this thread. robert.jensen@nwa.com (m-f 7:30-4:30pm cst) otherwise robert.jensen@frontiernet.com (weekends & after work). Thanks..

[TeCaTe_MaN]

you need a KX500 carbuerator!!!!

[200x Basket]

200X Basket -- The cylinder has K&K scribed in it. What the heck is that all about? Did you sell it on eBay to rpjense? You ran this cylinder on an otherwise stock Tecate (carb, pipe, etc)??


KK stands for custom kraft. the cylinder is not your problem. it is either still flooded, timed wrong, bad stator, or really out of tune carb. the kx and kxt engines are the same except the tranny, cylinder, and ignition. the timing is the same. i run the kx ignition on my 86 tecate.

[ange]

It's the stock 34mm. I'm curious about using the KX ignition. Did they recommend the KX ignition because of the lighter flywheel? Or is the timing different?? 38mm flat slide = $200 (plus jets, slide, needle), KX ignition & flywheel = $250. Ouch! This experiment is getting spendy. If someone wants to make me an offer, we should do it outside of this thread. robert.jensen@nwa.com (m-f 7:30-4:30pm cst) otherwise robert.jensen@frontiernet.com (weekends & after work). Thanks..


The JWR manual says "Use the stock Tecate ignition, replace ignition coil w/ a KX motocross coil because the ground system is more reliable under race conditions"
Thats all it says.
I really dont think you need a bigger carb, or any other stuff that people are suggesting. It's all in the carb tuning (and cleaning). I know it's a pain in the ass, I have been doing it for the last couple weeks myself.

[sean8231]

I finally finished my motor rebuild (which included a kx topend), I am using a 36mm flatslide from an 89 trx250r.. I'm using all of the kxt electronics, no change in the timing... And mine started with 2 kicks.... Few bugs to work out, but runs... I wouldnt worry about switching over to the kx ignition system( I thought they were the same other than the kx has no headlight capability).....

[200x Basket]

the ignitions are way different. lighter flywheel, no magnets, no lights, and you can feel the power difference

[TeCaTe_MaN]

ah hem...the guy i went riding with did this to his bike...he had similar problems with starting it so he threw on a KX500!!!!! carb and it worked cherry and ran great

[rpjense1]

Ok, you guys talked me into it. I've got a Ricky Stator & Flywheel, so I'm confident the ignition is ok. I assume the 36mm & 38mm Mikuni slips into the same spigot as my 34mm? Bad assumption? If someone has the JWR 38mm flat side carb specs, (mj, pj, needle, clip pos) that'd be great. What the heck, I have another month until summer.

[200x Basket]

i would use a 34 or 36mm (cant remember) PJ flatslide from a 86-89 trx. i run a pwk 39mm on my 86 tecate. i would nut use a mikuni 38mm flatside as a paper weight. they are impossible to tune and run like crap.

[Jeb]

My 38mm Mikuni was jetted right on for my 84 Tecate with a DG Pipe/Silencer, vented airbox with UNI-Filter and Boyessen reeds. I personally never had a problem with mine. The trike started easy in one or two kicks, even cold, and once warmed up it had great throttle response through out the rpm range. No hesitation and no problems on top. As far as I can remember the 38mm mikuni slipped into the stock KXT intake boot. I've never ran anything but the stock carb on my 86 and it's state of tune has never been as good as what my 84 KXT was. Whether this is the norm or not i have no idea. It's just my own personal experience.

Check with Joel (TecateCrazy). I gave him my jetting to use as a starting point only since the trikes were modde'd similarly. He might still have the info. I still have the carb same condition as the day I pulled it from the 84 KXT. I'd like to get it onto my Tri-Z. I'll have to re-jet the mikuni and the Z's stock carb is tuned fine and I hate to mess up a good thing plus I need a bigger throated Clamp-On filter. Anyway I used to have the info in a pm, but it was lost when the board was upgraded. Maybe Joel still has it.

[tecatecrazy]

Jeb as far as I remember you were running a 290 main and a 45 or 50 pilot with needle 1 from the top which seems to be a shade rich for me but its a good starting point. I am running a 38 TMX, dg header, answer silencer and a v force reed block on a brand new kx cylinder (thanks NICKG). I am not very comfortable with my jetting skills so have no good advice on proper tuning. good luckl with it! ---Joe

[rpjense1]

My '85 is bone stock except for the cylinder and a DG silencer. I'll keep my eyes peeled on eBay for a 38mm flatside. If anything, the carb specs listed by Tecatecrazy might be a tad on the rich side due to the lower air flow of the stock pipe, airbox, etc. Then of course this cylinder has some type of K&K porting done to it, so it's hard to say where I'll be at. I'll give it a shot and see what happens. Thanks for the help guys!

[wizzard]

did you clean the carb? none of the other things your looking at, (timing, jetting etc.) allows for enough adjustment to stop the bike from starting.
Don't give up.

[DuneRunner]

I have a 84 KXT250 with a KX250 cylinder and head. At first I tried the 38 flatslide but could never get it to run right,so I went back to the stock carb and it ran like a bat out of hell.I had to play with the jetting but not much. I let it set for about 3 years and when I tried to start it ,it gave me all kinds of problems, it turned out the float was sticking. After a carb rebuild it ran fine,starts up with one to two kicks.

[rpjense1]

Geez; Do I feel stupid....

It was the flywheel key that had sheared off. Weird? I remember my trike running at the end of last season before I put it away?! Then when I found water in the tranny fluid I tore it down and noticed the scored cylinder. Strange how the flywheel key sheared off? Usually they stop dead as a doornail? Anyway, the trike seems to run extremely strong, even with the stock carb. In fact I was hesitant to open it up much above 1/2 throttle (on the street) because the front end wanted to come right up. The power seems really strong down low too? The early 80's KX250's must have been really torquey?

I'll haul it to the track this weekend for break-in and see how she does... Thanks guys!

[eh_tee_see]

thats awesome... that thing will be bad :(