83' 250R Piston still siezing.

[leetwanker]

Well, I just got my engine back from a local ATV shop, after having the cylinder resleeved, chamfered, new piston and rings, they replaced a couple seals in my bottom end because they thought I was pulling extra air through one, causing me to go too lean and sieze. Anyway, they were very aware that I was siezing piston after piston and were extra careful about making sure the tolerances were all exact and all that.

I put the engine in last night before I went out drinking and started it up for 10 or 15 minutes and let it idle. This afternoon I started it up and let it idle for 20 minutes. A couple hours later I took it for a 5-10 minute ride around the property here, let it sit for another couple hours. Just now I was planning on taking it for a 15 minute ride, and the last of 4 heat cycles, 10 minutes into the ride I was driving down a dirt road at about 1/4 throttle, being real easy on her, when, same as always, the engine starts losing power and the rear tires lock up. I sit on the side of the road for 5 minutes and start her back up on the 2nd kick and drive it home. It's getting to the point where I'm scared to drive it for fear of my wallet becoming even emptier than it already is.

Anyone know what could possibly be causing these problems? The ATV shop just went through my whole engine and inspected everything and only found 1 bad seal and replaced it and another seal just incase. I'm running 20:1 Golden Spectro (which I'm told I only need 40:1 but I'm too scared to run that lean a mixture if I'm siezing up at 20:1). I'm running 87 Octane fuel.


Thanks all.
Justin

[Billy Golightly]

What brand piston are you using, and what is the piston-cyl clearence at? (I know the shop did it right, but for the sake of being thorough lets see what it is)

What are your carb specs? Main, Needle (including clip position) pilot, and idle screw jetting. Stock carb or other? Is your exhaust by some weird chance clogged up? Any dents or rat nests in the pipe, is the muffler clear also? Use lots of compressed air to test it out, around 90-100lbs of pressure if possible.

Also...has your cylinder head by some chance been re-domed, And what spark plug are you running?

[Pete]

lean jetting probably. I would also run at least premium fuel, 87 octane is garbage. Running a richer oil mixture actually leans out your jetting slightly (less fuel)

what does your spark plug look like?

I would also recommend having the engine leak tested.

[Bryan Raffa]

is it gettin real hot? water pump workin?

[firefirefire90]

air cooled trike raffa....couldn't it be something in the lower end and not the top end? Or is the piston literally siezing in the cylinder by itself?

[leetwanker]

I'm using a Wiseco standard bore piston with two thousandths clearance at the bottom and slightly more at the top of the cylinder. (the ATV shop guy says the bottom wears quicker so he did that for the bore to last a bit longer.)

My Jet is a 135 in the stock carb. My clip position is 1 down from the middle. It was in the middle position when I bought the bike. I'm not sure what my pilot or idle screw settings are. I rebuilt the carb about 1 month ago and put everything in the same amount of turns out as the old stuff.

I don't know how my exhaust could be clogged up, exactly how should I test this? It seems like it's flowing fine, but this is the first 2-stroke bike I've ever owned. None of my exhaust is dented. it's an aftermarket DG Pipe and Muffler.

I don't think my head has been redomed, it looks stock, but I can't be sure. My plug is an NGK BR8ES.

From looking at the plug it's a tan color, sometimes a little oily, the heat range looks good on it. The plug definitely shows a rich mixture if anything, and I'm too scared to go and try to lean the mixture out.

I don't know how to test if the engine is overheating, but I'd definitely like to do that if it's at all possible.

It's definitely the piston siezing up, I've had the cylinder off lots of times, once after a brand new sleeve and piston were put in and it's quite clear, it's siezing up at the 4 corners (i'm guessing this 4 corners thing is common). The good part is, It's been hardly scratching my sleeve, the piston is getting tore up when this happens though.

[Bryan Raffa]

oh ha ha ha ha ha! duh! guess your not really pushin any water then...:lol: :lol:

[Bryan Raffa]

that 4 corners deal happens alot when its not warmed up enough.called cold seasure..quite common

[leetwanker]

that 4 corners deal happens alot when its not warmed up enough.called cold seasure..quite common

A cold siezure after the bike's been running for 10 minutes? strange.

[leetwanker]

The threads on the plug are a bit oily, there is a bit of carbon buildup on and around the side electrode, the rest of the plug is rather shiny. This is the best picture I could take of it.

http://i79.photobucket.com/albums/j128/JustinWPB/DSCN0038.jpg

[BigGreenMachine]

Steel sleeve won't heat/expand as fast as the aluminum piston. My Tecate did this to me twice with the steel sleeves I had installed. Was running for about 10 minutes and got the same damage as you...running at a little more then half throttle when I start losing power and it locks up.

Also you may want to go with the 50:1 ratio. Quality synthetic oils are designed to run at those limits.

If your jetting is stock then you can rule that out.

[Billy Golightly]

Your lower end range of the carbueration might a little rich while the upper half is lean, making the plug hard to read. Pull the needle and slide out and check the actual #s on the needle (Should be something like DEG, DEK, etc) You might for kicks, try riding it with the choke on and see if it seizes again.

[200x newby]

is it the piston siezing or the wrist pin siezing? you might want to put a little bit of motor oil down where the crank and rod meet for extra lubrication i did this with my 77 rm80 and it runs just fine if not better. it will sling the oil on to the sleeve and wrist pin bearing to help it from siezing. just a thought though

[leetwanker]

is it the piston siezing or the wrist pin siezing? you might want to put a little bit of motor oil down where the crank and rod meet for extra lubrication i did this with my 77 rm80 and it runs just fine if not better. it will sling the oil on to the sleeve and wrist pin bearing to help it from siezing. just a thought though

There's oil in the crankcase lubricating the crank and bottom of the rod, the top of the rod must be getting oiled by that oil also I would think, else it would lock up real quick due to it being a sleeve bearing.

Since I was heat cycling the engine at the time, I was hardly ever going past 1/4 throttle, maybe hitting 1/2 throttle at most.

Billy, I'll try giving it a ride with the choke on tomorrow if I have a chance, see what happens.

[Dirtcrasher]

Do you keep using the same brand of piston with each rebuild??

[Pete]

I think 2 thousandths is way too tight for an air cooled motor. I would double that in an air cooled motor.

[leetwanker]

Do you keep using the same brand of piston with each rebuild??

Wiseco is the best brand is it not? But yeah, thats all I've been using.

[leetwanker]

I think 2 thousandths is way too tight for an air cooled motor. I would double that in an air cooled motor.

I would think the shop I took it to would know the right tolerances, I've been taking my bikes to him for close to 20 years. Any pros around to throw in their .02?

[Pete]

I run my water cooled R at 2 and a half to 3 thousandths, which is the clearance stated directly on the Wiseco box. If I need to run the motor hard immediately I will do up to 4 to 4 and a half thousandths.

[SYKO]

I second that, the shop that bored my Gf's blaster told me that as well, and it hasnt skiiped a beat and she runs the hell out of it.

[Erics350x]

that plug looks dry to me. try cleaning the petcock and rejetting. also back off to a BR9ES plug

[Maico]

Bore the cylinder to whatever pistons specs you're using...in this case,Wiseco. .002 is too tight. Tapered bore ?? Find another shop. That's rediculous. It makes sense in theory but doesn't work in reality. Tight at the bottom and loose at the top?? Where was this .002 measurement taken at ?? Don't let it sit and idle any more than to warm it up. You need to put a varying load on it otherwise it will glaze the bore and the rings will not take a proper seat. You need to do a leak down test before you fire it up. Just because they replaced a seal doesn't mean it's not sucking air from somewhere else.

[InPiEcEs]

.002" is way too tight for an air-cooled 250, especially with a Wiseco in it.
That is where the problem lies.
Should be boring the cylinder straight. I never heard of using a tapered bore, but it's possible.
If the jetting in your carb is stock, it may need to be changed for that DG pipe.
Back to the top end though. I would go .0035-.004" on an air-cooled Wiseco.
They expand more than a cast piston, and differently also.
I learned the hard way on a '77 CR125M about the difference in water-cooled, and air-cooled bikes.

[leetwanker]

Thanks so much for the advice guys, it's absolutely amazing the incompetence I've managed to run across trying to get my damned bike running!

Does anyone know a good motorcycle machine shop that knows what they're doing in south florida? I'd be willing to drive up to Ft.Pierce or down to Ft. Lauderdale to get it done right once and for all.

Also, could I do a leak down test myself? I'd really rather not have to put that engine back in my bike once again, it was a *Edited**Edited**Edited**Edited**Edited* to get all the suspension back into place.

[Billy Golightly]

TDR (Tony Doukas Racing) http://www.tdrracing.com/tdrracing/index.htm just did the cylinder for my flat tracker and seem to have done a really nice job. If you send YAMAHONDAMAN a PM, he might be able to hook you up with a special price for a bore job and piston done there.

Instructions for a leak down tester: http://macdizzy.com/leakdown.htm

[oldsking86]

Man I haven't heard of TDR in ages, how big did they go on your R and for how much roughly? PM if you don't want o spread the details haha

[Billy Golightly]

Well I got special dealer pricing that I don't think I'm suppose to reveal, but the piston in it now is 68.5mm from a YZ250 :)

[Tyler]

I never ran a Wiseco that tight. In a water cooled motor I ran 5 thousandths and never had an issue. Let the cylinder get warm to the touch then ride it. 10 mins is way too long to let it idle. I thinkl your jetting is a bit lean. That tapered bore idea is not a good practice. Straight bores make power. Forged pistons need room to grow. With todays good oils 40:1 is fine. check and double check for any leaks spray WD 40 around areas to check. Seek and ye shall find!

[leetwanker]

TDR (Tony Doukas Racing) http://www.tdrracing.com/tdrracing/index.htm just did the cylinder for my flat tracker and seem to have done a really nice job. If you send YAMAHONDAMAN a PM, he might be able to hook you up with a special price for a bore job and piston done there.

Instructions for a leak down tester: http://macdizzy.com/leakdown.htm

Oh crap, I just went to TDR's site thinking I was going to have to ship my cylinder off, you didn't mention they were in Pompano! :w00t:

Thanks Billy

[Yamaha Tri-Moto]

I'm having the exact same problem with my 83' R. Its in pieces in the garage right now, not sure what to do.

[leetwanker]

I'm having the exact same problem with my 83' R. Its in pieces in the garage right now, not sure what to do.

Sucks not having a bike doesn't it? I rode mine for about 2 hours after I bought it before I started going through all this and have spent upwards of a grand replacing piston after piston just trying to find someone who knows what they're doing.