'85 ATC250R Overheating Issues.

[lazerusrm]

Hey guys, need a little help here.

I have an '85 ATC 250r .20 over (i did the work muhself, as always)
i put on a coolhead 18cc dome
boysen 2 stage reeds
39mm PWK
Aftermarket pipe (unknown)
FMF Silencer..

When i first got it back together, i started with a pretty fat main (200) i slimmed it up a little to 185, and it ran alright, still seemed to bog at WOT, Plug chops were very black. I slimmed it down a bit more to 172. It ran great for a while.

But then i started to have overheating issues. I put a 180 back in to richen it up a bit, it hasn't affected the cooling.

My question is, i know the cooling system is in good order (This is a very clean 250r) i flushed it and filled it with water / engine ice, examined the pump, etc. The radiators are very straight with very little fin damage.

The dang thing will overheat cruizing at 25-30 mph with no light load after about 10 mins of riding on the street. Latest WOT plug chop reveals a very BROWN plug

I noticed i do have an exhaust leak, would that alone be enough to cause it to overheat badly? Are there any super secret tricks to bleeding the coolant system other than what the manual states?

The engine still runs very strong, it just overheats (250+) very easily.

The coolant does not boil until it gets above 250-260+ (somewhere in there) so i know the cap is good. (water temp gauge)

My 250R thanks you for your help :)

Brad

[Mosh]

Too rich or lean jetting can cause overheating.
The old theory on a 4 stroke was to richen jetting to help cool the engine.
However,on a 2stroke that does not work.

You did not mention what pilot jet you run.If not proper,that can greatly affect your mid range cylinder temps under cruising as you stated.
My 310 motor runs a pwk 39 with a 48 pilot and 175 main.It does pretty well on those jets.
For a 250 engine your main seems a little rich and whatever pilot you have, should be considered.
Another issue is the dome size.That 18cc dome requires race gas.You could be detonating if your octane is too low.
If you dont mind paying 6$ per gallon for 110 then run it.
But for a everyday rider a 20 or 22cc dome would be better.

1st you may want to examine your octane level.
2nd you may want to lean back your jetting depending on what you have for a pilot.
Last you may want to cut back you dome size,or maybe install the stock head.

[250rfan]

Hi,

Could it be possible you have a leak at the cylinder head gasket or the base gasket?, am assuming you do not have the proper tools to pressure test your cylinder after re-build.

If your water pump is faulty you will see coolant leaking from a small 'tell tale' hole just underneath the water pump casing housing. Unless the hole is blocked of coarse, which is possible.

Mmmmm,,,,why the monster 39mm carb:wondering,,,this IMO seems like slight overkill.

On a tuned 250 cylinder a believe 36mm is sufficent.

On a tuned 300 cylinder a 38mm is sufficent.

Are you running a standard or aftermarket (K&N) air filter?, are you running a airbox lid or not?.

Also, the aftermarket pipe you speak of, if its like a DG, these pipes are basically an OEM copy - so not much increase in HP, could it be possible your overheating issues stem from overheating on the exhaust port due to restricted flow?.

What the benefits of the coolhead on a standard cylinder?, can someone educate me on this :wondering.

If i were you, i would replace the 39mm carb with the standard OEM one and the exhaust, and start from there.

Replacing items one at a time.

[lazerusrm]

Forgot to mention i'm at 5,000FT altitude. 18cc dome is no problem here without race gas :) I dissasembled the head and found no signs of detonation or leaks. I examined the water pump assembly carefully, and all is well, everything looks brand new.

No airbox lid, Aftermarket K&N W/ Pre-filter ( i didn't put it on)

Reason for the 39mm is i might to a PV head soon on it :) I just had to rebuild it before it blew up.. (the STOCK piston was 3/4 cracked in half when i pulled it out!!)
I stole the stock carb for my other air cooled 250r

Its got a Size 60 Pilot in it.

Wouldn't a base gasket leak cause it to run funny? It idles perfect, has good top end, etc.
I cleaned all the carbon buildup out of the exhaust when i re-built it. I also bought the Trike with the exhaust on it, you'll have to tell me whether or not its a stock replacement.

BTW, it will overheat just the same on WOT pulls, too. Thanks very much for your input.

Pics coming up... 1 min

Brad

[lazerusrm]

http://img229.imageshack.us/img229/5323/sany0112tk0.jpg

http://img238.imageshack.us/img238/470/sany0111pl7.jpg

http://img50.imageshack.us/img50/2098/sany0114ft8.jpg

YES i have a flat tire, my brother ripped a hole in the sidewall

[Mosh]

Another thing you may want to check...
Pull your stator cover and see if there is play in the crank bearing.Sometimes they get worn and will suck some air past the crank seal,and lean out the engine.
There should be no play in the crank bearing,or up and down movement of the flywheel.

Even though your at high altitude,does not mean that you dont need race gas.
Your squish readings in the head still could be too high.

Nice trike,and KTM:naughty:

[250rfan]

Okay, am still not convinced on the 39mm carb,,,,but i am overseas at the moment and i dont have my jetting info on me, so i cant tell you what i run on my 300cc CT cylinder with a 38mm carb.

Now on the 2nd picture i can see you have the plastic coated clip which supports the stator wiring harness bolted to the side of the cylinder. That clip should'nt be there, it should be mounted on the left upper side of the intake manifold.

That bolt is for draining the coolant system and should have a copper washer there to seal, that could be an issue.

i'll talk to someone in the know and get back to ya,

[lazerusrm]

I checked the System for detonation on 91 octane fuel. There is no detonation, nor signs or sounds of detonation. the compresson ratio, even with the 18cc dome, i believe is still less than stock at sea level..

Anyway,

I'll move that bolt, i haven't noticed any coolant leak issues, but i will re-locate it to its proper home. I'll also check the crank for play, but i don't belive that is an issue, its a pretty low hour machine.

Any ideas on what pipe that is?

Would the pipe leaking cause a lean out issue?

Thank you so much for your help, i sincerely do appreciate your posts.

it does sound like i am running the carb very rich, though.

[DeePa]

how does the trike run when it overheats???

that guage is pretty close to the pipe

[Billy Golightly]

I'd run a leak down test on it before I went any further with diagnosis if it were me. I've ran a 39PWK on a bone stock 250R motor with bolt ons (stock bore, stock porting, OEM piston, I mean BONE stock) and it ran great.

[lazerusrm]

I think i found the problem....11 hours on this piston Note, noticably more scored on the exhaust side? I figured out i didn't have a base gasket leak... I pulled it off, and it when WHOOSH, when i loosed the last bolt on the Jug. :)

I also did check the Stator, The stator side is Very Tight, and Very Clean.

My guess is, machine shop F@$# up! What i don't get is the Scoring mark on the Intake Side

Whats the Piston to wall clearance req. on a Wiseco?? I measured (calipers) about .02" But i really need a Dial Bore Indicator (dont have)

The machine shop does use a Sunnen Boring machine... So i don't know...

http://img149.imageshack.us/img149/416/65861784gz2.jpg

Intake Side.

http://img241.imageshack.us/img241/9971/sany0116on1.jpg

[Billy Golightly]

WHOA!, .002 is WAY tight, it musta been trying to seize the entire time, the amount of heat built up from the friction of that close of tolerance was extremely high and accounted for your temps I'm sure.

In addition to the exhaust, that spot off to the side of the intake is also known as "4 corner seizing" can be attributed to just a generally too tight of tolerance or an oddly shaped bore. I'd run .0035 or .004 tolerance myself, but I like em a little on the loose side.

Can you post some pics of the cylinder walls too?

[lazerusrm]

yep, give me a min. Intake side isn't really scored too bad... Exhaust... TERRIBLE! I wasn't running the engine lean, i don't think. The intake side is hardly scored at all.

http://img47.imageshack.us/img47/6755/sany0118ha4.jpg

http://img239.imageshack.us/img239/3470/sany0117da0.jpg

[lazerusrm]

I measured again, clearance is about .03"

No detonation :) hahahah. The piston looks great from the top.. Maybe i should sell it on ebay. :naughty:

[250rfan]

Aaahhhh,,,well looks like you found your problem Lazer. :w00t:

Looks like your on the path to fixing it.


BTW,,,,sweet bike looks very original and well kept machine, worth keeping hold of, the aftermarket pipe is cool,,,,looks like an old scholl sectional, again nice!

Oh ye,,through some pics up of your KTM, THAT THING LOOKS BADASS!!.

[Mosh]

If I remeber right,Wiesco calls for .002" Of piston clearence,But I agree with Billy,Most guys will open that up to >004".
The ring End gap should be .004 For every inch of bore diameter.

It looks like A classic case of cold sieze to me.The piston heated up before the cylinder wall and siezed down.
When you reassemble,double check all tolerances,And be sure to Run the motor easy for at least 4 hours with a couple of cool down cycles.This will help break in the parts.Also be sure the engine is at full operating temp before ripping on it.This will help prevent cold siezing.

[Billy Golightly]

And I'll probably get crucified for reccomending this....but consider using a high quality casted piston (Like a Pro-X)

[Mosh]

No I agree Billy,they are better pistons.

[lazerusrm]

Wiseco runs fine in my air cooled 250r.

Im having him run the clearance at 004 Rather than 003 (where it was at)

Im having him mic the old piston to see if it was overheating related. I'll post some pix of my ktm for 'yall. :D i just bought it 2 weeks ago, its my main machine now (But i switch off)

I think now i'll run a mix of race gas in it, just to be safe, even though i haven't been having detonation problems, also i'm having the head checked for flatness as well..

I don't want to rip this thing apart again after 12 hours of run time.... UGH

Brad

[250rfan]

Glad you've hopefully found the solution Bradd.

Moshes advice on the pre warm up is very good, i'd forgot about that.

The answers to your post have refreshed my memory some what, hope the 250 works well for you.

Know lets see those KTM pics:naughty: :naughty:

[lazerusrm]

Yes, the 250R is in great condition. the whole front end has been polished (handlebars, triple trees, etc.) it rides like new, it has a trx450r rear brake (i think) and some other stuff.

I usually am very careful to get coolant temps to 150*F Before running it. BUT, others have been riding it since the ktm. At any rate, i already bought a new piston and gasket set, and it is at the machine shop getting re-worked, it will be ready tomorrow.

What is the Maximum i should allow the coolant to become? Anyone know where i can get an exhaust sealing ring?

Here is my KTM 525 XC... Soon to be big bore. :) I have a 540 kit on order, i'm considering getting some crank work done to get it out to 576 or so.. we'll see.

By the way, i admire your 450R Trike. Its very nice. If you want some vids of the 525 just ask, i'll get some up :) (I'd be happy to do some of my 250r when i get it back together, too)

http://img165.imageshack.us/img165/228/sany0119jq0.jpg

http://img47.imageshack.us/img47/8735/sany0120lm9.jpg

[250rfan]

Yes, the 250R is in great condition. the whole front end has been polished (handlebars, triple trees, etc.) it rides like new, it has a trx450r rear brake (i think) and some other stuff.

I usually am very careful to get coolant temps to 150*F Before running it. BUT, others have been riding it since the ktm. At any rate, i already bought a new piston and gasket set, and it is at the machine shop getting re-worked, it will be ready tomorrow.

What is the Maximum i should allow the coolant to become? Anyone know where i can get an exhaust sealing ring?

Here is my KTM 525 XC... Soon to be big bore. :) I have a 540 kit on order, i'm considering getting some crank work done to get it out to 576 or so.. we'll see.

By the way, i admire your 450R Trike. Its very nice. If you want some vids of the 525 just ask, i'll get some up :) (I'd be happy to do some of my 250r when i get it back together, too)

http://img165.imageshack.us/img165/228/sany0119jq0.jpg

http://img47.imageshack.us/img47/8735/sany0120lm9.jpg

Man,,,,, that quad is plain SICK!!,,,:Bounce :Bounce , if am going 4 poke quad i'm having one!, is that standard OEM?.

Okay, as far as the sealing ring for the 85, Oem is a metal ring - which leaks:( so for a true seal you will need to go aftermarket - double O ring, check out ESR.

As far as temp, i dont know, i usually just give my bikes 10mins or so to 'warm up'
however my brother just jumps on his trx and thrashes the s**t out of it, after 2 years of non use - dont figure!,,, i normally turn to my father and say 'he's going to cold seize that', but the lucky fooker never does:wondering...
Thats life a suppose.... keeep me updated on you Ktm tuning am well interested.:welcome:

[lazerusrm]

The KTM Is bad Ass, It is even faster than my 250R.

Its 100% factory at the moment (front fender flares removed, designed to do that)

i'll look for an aftermarket flange, that may have been the cause...

Cool, i bought a billet flange and a case saver (it was missing)

Hopefully that fixes it....

BTW, Dont buy any other quad but the KTM. Its the best ( and near the lightest) It definately comes with the best stock components.

Tell you what, bring your 450r trike, and we'll trade for a day. :D

[250rfan]

The KTM Is bad Ass, It is even faster than my 250R.

Its 100% factory at the moment (front fender flares removed, designed to do that)

i'll look for an aftermarket flange, that may have been the cause...


Woooow, i dont think the problem is the leaking flange dude, just giving an answer to your leaking manifold problem. :)

The replys and advise from Moshman & Billy are the true answers to your problem.
These guys have far more experianced than me, when it comes to 2 strike tuning:rolleyes: :rolleyes: ,,,there both freaks!!!:lol:

Gordon.

[lazerusrm]

Yeah, i'll definately accept their advice. I will consider a PRO-X Piston for the /NEXT/ Build.

I can buy the wisecos here locally, so i didn't want to wait, because the weekend is almost here... :)

The flange is only 50 bucks, so no big deal. I'll definately be sure to double check the clearances on everything (they were in spec on the previous build)

THANKS GUYS My 250R <3's u.

[HondaHarry]

looks like a part of the problem is that the ports werent chamfered...
if they were, they dont show up in the photos very well.
I cant see any relief grinding at the exhaust bridge either.
and with the heavy scoring on the piston, I would suspect that started the failure, if it hadnt seized, there was a good chance of it catching a ring later on... HH where ya located in utah lazerusrm? Cedar City for me.

[lazerusrm]

Im in Highland, Moving to Park City.... As soon as my house closes, but you know how the markets are right now... ugh.

Yeah, i SUSPECTED that too, but they told me it was fine... Any articles to recommend me to do it myself? i''ll have a look with mr. google, too.