Tecate chokes UPDATED pg. 3

[Xpress]

So my bike is choking when it nears WOT. It hasn't ever done this before.

Carb is clean as a whistle (it idles and snaps open just fine), air filter is new, reeds are clean, new exhaust gasket (it was leaking before, though that was the problem but nope).

The only thing that I can think of is it's the oil I am using. It's Valvoline multi-purpose oil, which a few pinger guys have told me works great. It has only started doing that just shortly after switching to that oil.

The plug is also a dark dark brown, almost black color, which says it's running rich.

http://img34.imageshack.us/img34/3845/mg8886.jpg

The carb I have is a Mikuni 38mm flatslide- is there a way to lean it out with the mixture screw, or idle screw, or do I just have to re-jet?

Also, spraying ether around the gaskets and intake boot yield no change in idle. Only idle change is directly into the airfilter. 32:1 mix.

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Another Tecate issue. It's a buddy's bike, if you snap open the throttle, it bogs down and starts backfiring. I haven't gotten a chance to really play with it, other than slapping a known good intake boot on it and cleaning his carb out, but my guess is it might be running LEAN? If you ease into the throttle, it kinda goes, but then it bods down. He is using this weird orange pre-mix oil in it.

His TRX250R is also having issues. It has no powerband, goes right up to it but doesn't go any further. Same pre-mix oil too, both bikes are at 32:1. You can't ease into it either. I thought it might have been the airbox lid, but after removing it, the bike produced the same results.

Any thoughts or suggestions?? This guy is stoked that his Tecate is running, but it'd be really nice if he could tear it up with me on the trails without his bike giving him crap.

[audioworks04]

Sounds to me like both tecates are rich, and need rejetting. Personally I would runner leaner than 32, I run 44:1 in all of mine and mr R has 8 years on a top end and still has stock crank from 86. I would try a leaner mix, and use a known good oil like klotz or ams with 91 octane. You can try tunning with just the mixture screw, but that really only adjusts your pilot jet, so if your problem is in the mid to high range, it will probably yield little results. When I jet I like to do plug chops, find a gravel road or a long strait stretch and get into atleast 4th wot, shut it down and pull the plug, you can then throw another plug in it and ride back to somewhere to do your actual chopping. Always use a new plug for each chop.

[Xpress]

So if I run a leaner mixture, it should start to clear out, you think?

[fabiodriven]

So if I run a leaner mixture, it should start to clear out, you think?

I don't think the oil is going to have that much of an impact on how it runs.

[Slingblade]

^ I agree. Try going down on the main jet a size or 2. Summer is officially here, hot weather = rich condition in a finicky 2 stroke.

[86T3]

Check your stator, thats pretty much what mine did when the it started to go

[just ben]

pretty sure oil has alot to do with how a 2stroke runs there fabio. everyone on here seems to think too much oil is better. not so much too much oil leans the fuel to air ratio. which means your engine is lean, not rich because it smokes alot! what happens to the unburned oil when you put too much in? it sits in the engine base also in the exhaust.ditch the gas station oil and spend the dough for a good synthetic.I run amsoil interceptor at 50:1 never a problem

[fabiodriven]

pretty sure oil has alot to do with how a 2stroke runs there fabio.

I'm pretty sure I'm going to stand my ground. I've been wrenching and riding for many years and I don't even measure my two stroke oil most of the time. My Tecate has always run spot on and the Jug I took off last year still had the original Nikasil and ran fine.

[just ben]

I'm pretty sure I'm going to stand my ground. I've been wrenching and riding for many years and I don't even measure my two stroke oil most of the time. My Tecate has always run spot on and the Jug I took off last year still had the original Nikasil and ran fine.

as long as it works for you. not trying to get anything goin the info I posted is factual and I stand by it. running fine is not the same as running good or great

[fabiodriven]

And we're trying to get his engine running right, not tuning it for the drag strip.

[Xpress]

Well tuning for the drag strip would be nice ;)

There was one point when I was riding it around to dry it off after washing it, that it opened up all the way and ran great for all of 2 seconds then it choked and bogged a bit.

I just thought about it, but I have a stock mikuni carburetor sitting in my basement, which what I believe to be stock jets. Those jets should fit on right?

The bike was jetted properly when it had the DG exhaust on it. Now it has the stock exhaust, because the DG has a nice custom rock dent in the header section :rolleyes:

[fabiodriven]

You didn't say you changed pipes. That's more than likely your problem.

[Xpress]

So then too big of a main jet then yeah?

This issue only started just recently, otherwise it's ran fine with the stock pipe. What's the stock main jet, 340?

[just ben]

340! whoa i think its 230 could be wrong

[Xpress]

Looking on dennis kirk, it says the stock main jet is 340 for the 38mm flatslide. Mikuni says that the stock main jet size is good for stock pipes. I'll see what it has on it tomorrow..

[just ben]

ah sorry forgot you said it was a 38. 340 seems pretty big even with the bigger carb. do you know what size is in it?

[Xpress]

It has always had the 38 mikuni on it for as long as I've had it. Also I always run 87 octane, no need to run higher than that on a stock engine.

[fabiodriven]

I didn't see that you're running all purpose oil. That's a big no no, but again, not the reason for it running bad.

[hadar]

I think your carb is too large for a stock kxt cylinder. A 38 mic would work fine with a proted big bore or 83-84 kx cylinder but with a stocker I myself didn't have much luck. I couldn't get my stock jug to run right with the 38mm. It's like pushing a tennis ball through a garden hose. Just my $0.02

[Xpress]

The problems arose just recently. First tank of multi-purpose oil was fine, now it chokes near WOT.

The jet that was in it was a 320, and the only other jet I had lying around was a 230 from the stock carb. Tossed it in for the hell of it, and the plug came out copper after some wide open sorties. Still need to do a proper plug chop though. Felt good, until it got wide open.

Guess i'll just pickup some AMSOIL today and give it a whirl.

[nd4speed]

i run valvoline 2 stroke oil without issue.

This weekend was hot and humid for me and I had the same issue. Thought either rich or slipping clutch. Well day 2 and the plug fouled and was black like yours. I'm guessing it was too rich for the weather now. 38mm PWK with 155 main.

A 340 main for 38mm mikuni is probably too big. I ran 280-300 summer-winter in my 84 and 86 Tecate/KX250. 38mm TM and a VM also i sold.

[just ben]

the all porpose oil is way better than the oil that was available back in 85 but would recomend a good synthetic. with that thing being jetted that rich it is possible that there is an excess of fuel/oil in the crank. if you dont know fuel on a 2 smoke goes through the bottom end before it goes to the combustion chamber. since there is no drain for the case,the only way I can see to drain it or even see if thats goin on would be to pull the carb and boot ,make sure the piston ports are lined up with the intake and tip way back. only other way would be to pull it apart

[Xpress]

Made the 15 mile round trip to the local motorcycle warehouse and picked up a quart of Yamalube. I saw they had Amsoil too, but I figured that I wouldn't waste $12 on a quart of oil only to find it didn't solve a thing, since Yamalube has worked for me in the past. And it was on sale for $3.49 ;)

Mixed it up 32:1, drained the old stuff (I'll use it for the leaf blower) threw the new stuff in and off I went. Pulled great all the way to the topend, except it kinda drops a tiny bit in the mid with the power, but picks up on the top. Runs better than before, like a bat outta hell.

So I guess the problems were a combination of everything. Dirty air filter (I knew this was part of the problem anyways), dirty carb, too big of a main jet, and wrong premix oil.

[just ben]

good to hear its goin again. put the gas on the fire pit I dont wanna see a thread for the leaf blower lol!

[Xpress]

Na I don't care about the blower, although it likes 40:1 not 32:1 :lol:

[Xpress]

Still running a bit rich I believe. After about 5 minutes of riding, it started to bog if I got on the gas hard. Also, I discovered that the carb is a 34mm flatslide, not the 38 I assumed it was. I verified this through a highly complex process of comparing the stock carb and the flatslide :lol: Although the flat slide has a bigger air filter size..

It had a 320 in it, now it has a 230 main. What should I try next?? The plug comes out as a very faint dark brown. I know it's not a proper plug chop, but it still says it's rich.

[nd4speed]

Mikuni TM 34mm standard jetting is 220-240 main for summer-winter. That's just a standard and every bike is different but that's what I used on that carb TM and a few LT250R motors.

[Xpress]

So maybe I should try a 220 main then. It seems like it's close.

[zzmegad]

seems weird tho that it was running good before and now you have changed the main by almost 10 sizes... How long was it running good for before?

if you think its still rich thats what your supposed to do make changes 1 or 2 sizes at a time until its right

[Xpress]

It hasn't ran like this since I have had it.

Before it had another engine with a KX cylinder, a DG exhaust, answer silencer, and the flatslide. Now it has a stock engine, with stock pipe, a general slip on silencer and the flatslide. The pipe got the rock treatment and is dented to hell on the header section, and the KX cylinder engine has really low compression.

[zzmegad]

dammit man that info should have been in the first post... get yourself some jets and get her tuned in. not too lean tho lol you'll end up like me :[

of course your gonna need to rejet, you changed the cylinder and everything

[fabiodriven]

dammit man that info should have been in the first post...

I know, right?

I swear you do this stuff bass ackwards sometimes just to start a thread Xpress...

[Xpress]

Heyheyhey, It didn't even occur to me until just before my last post that the previous engine had a KX cylinder on it. Totally different engine in it now, all stock.

Yeah, I'd rather run rich than lean. Too many horror stories. I think I'll try a 220 jet, it seems fairly close.

[bkm]

I'm not trying to bust your balls or anything, but how could it have slipped your mind that it now has a different engine and pipe/ silencer combo and you can't figure out why its running crappy. Just saying!

BTW there is absolutely nothing wrong with Valvoline oil. I used it for years and beat the snot out of my R and never once had an issue. Just because the price on the bottle is three times less than the good ole syn. stuff, doesn't mean its junk. People get to wrapped up with the price on the bottle and start automatically thinking that on oil must be junk because it doesn't cost as much as the fancy stuff.

[Mosh]

I remember back in the ole days when Tripod Troy would run that Tradco 2 stroke junk from the 7-11, or Quaker state Outboard marine oil in his 250R becuase that was all that he could find on a Sunday morning.
It was cheaper, available and he rode with it, but always needed a handful of spark plugs for the afternoon. I guess the oil was cheaper, but then he spent another $8 on spark plugs. I guess in the end it all evens out..LOL
Being young and broke sucked, and we did not have the internet to turn to for advice.

However, I would not run 87 grade gas in any 2 stroke bike or ATV.

Fabio..Looks like you got your signature request..LMAO

[ezmoney1979]

Im confused? http://www.3wheelerworld.com/showthread.php?132583-Seeking-engine-experts&p=1029927#post1029927 Post number 5. Is it running incredible or not?

[Xpress]

It runs fantastic. Just bogs if you SMASH the throttle open which I have concluded is because I am off by a jet size or two which I have concluded in previous posts.....

I don't know, maybe people just skip to the last post nowadays??

Glamy, my dads 84 4-runner manual says to run 87 octane :p

[Xpress]

Pulled out the reeds tonight to check them and see if some were bent. Sure enough, the 2 center ones are bent up and there is a 1mm gap between them and the plate. So needs to get some new reeds. Also it has a 230 main in it right now. From what I have read, the stock main is a 220, so I ordered up a $3 brass chinese equivalent 220 main jet to try out. If it works, I might leave it or buy a genuine Mikuni jet. This is telling me that the PO re-jetted for the DG pipe on the stock carb.

Need to pick up a few spark plugs too. I feel that I am close to a problem free bike. Except I need a new rear master brake cylinder.. :rolleyes:

Runs just fine if I don't mash on the gas like I like to, but I'm parking it until I get the jet and new reeds. Good thing my 200X runs great.

[Xpress]

Got my 220 main jet in the mail today, popped it in and kicked the bike over. Took several kicks to get it started and when it did fire up, it did not rev up at all, even after letting it warm up. I did not ride it, but it wouldn't rev up whatsoever. Every time I got on the gas it popped at me and bogged down. Can't ease it up either.

So a 230 main is too rich, but a 220 main is too lean?

So now I'm stuck with yet another bike that doesn't run right. I'm completely out of ideas now. And I did check the reeds, they seem to be fairly snug and tight. Might just sell the pos to the scrapyard, because that's all it's worth to me right now.

[muthey]

is that the Chinese jet or is it an actual mikuni?

[Xpress]

It's a chinese from Jets R Us. I wanted to try it first before buying an OEM so I don't waste more money than I have to. You see, being unemployed makes money kind of tight :( ;)

[just ben]

how cheap could the chinese jet be? mikuni jets from the shop I go through are only 2 bucks each.you only mention the main jet, which is fine because that rpm range seems to be were the problem lies. however you only changed the jet and went down like 20 sizes(think you said 320 to 220) The needle only works within a range of jet sizes. also bigger carb means more air. more air =more fuel,more fuel= bigger jet. I would start a couple sizes over stock and make sure you have the right needle for that jet. get the it close and fine tune with the clip on the needle. or since its a stock engine get a stock carb and set to the factory settings

[Xpress]

I have a stock carb, but it needs to be rebuilt. The engine side of the carbs are the same size, but the air filter side on the flat slide is way bigger, probably 6mm or more.

[nd4speed]

i went through a scenario like that recently where I thought the needle was wrong size, but I ordered the exact same needle cause I didnt know how to read (their numbers). I was bummed but anyway I put the new needle in and my problems vanished. Seems previous owner bent it or somethin. Looked fine but ran like crap. I was unemployed too and had time to fool with it, but only one could guess at the problem cause the needle looked fine and the carb looked barely used.