2-stroke engine problem

[F5 Dave]

Best take the cylinder off for a proper inspection. Check the powervalves & the exhaust ports, they can crack between the sub & mains, erm or the side & transfer?. . .Memory accessing picture in head & I can't remember, but if there is a crack you will see it under close inspection.

If this has happened of the plating has been damaged it can be repaired by someone like US Chrome fairly economically.

Dry clutch is SP model. I'd love one, but they are high maintenance & lets face it ageing a little for a performance engine.

[Number 5]

Ok, lower cyclinder has no compression, acording to the finger test, ther is noticable difference between the two wen turning the engine over,
ill attempt at opening the head later today, and take a look at the piston, where can I go buy new pistons and parts from?
and what else would u recomend i change while its in peices..?

Sure does sound like you have holed a piston.
I had frequent holed pistons when I raced 2 stroke Yams, the cure, after replacing piston and other damage, was to use 2 spark plug washers under each plug.
This moved the flame path of the ignition a little further away from the piston crown, no loss of performance but certainly cured the holed piston syndrome.

[Marls]

Sure does sound like you have holed a piston.
I had frequent holed pistons when I raced 2 stroke Yams, the cure, after replacing piston and other damage, was to use 2 spark plug washers under each plug.
This moved the flame path of the ignition a little further away from the piston crown, no loss of performance but certainly cured the holed piston syndrome.

True cause i replaced the spark plugs, not long ago well, roughly 300k ago, because the last time i had a problem, it was the plug on that cyclinder, and they are NGK BR9EIX iridium....$23 a plug....
I think its a hole in the piston aswell, from wat i can sence, but ill put some pics up when i start takin it apart... i will have to take the whole engine out of the bike anyways, ya?
any particular order to do it in?
usualy i work on cars, so hopefully bikes are simpler

[k14]

True cause i replaced the spark plugs, not long ago well, roughly 300k ago, because the last time i had a problem, it was the plug on that cyclinder, and they are NGK BR9EIX iridium....$23 a plug....
I think its a hole in the piston aswell, from wat i can sence, but ill put some pics up when i start takin it apart... i will have to take the whole engine out of the bike anyways, ya?
any particular order to do it in?
usualy i work on cars, so hopefully bikes are simpler

I hope you got the correct plugs. If you got ones that are too hot then you can burn a hole through the piston. If you got ones that are too cold you can sieze it too.

Let us know what the deal is when you get the head off. It could be so bad that it may not be worth even rebuilding it. Hard to say. Not sure about parts, yamaha shop will be able to source them I think but may be cheaper to buy from overseas.

[Conquiztador]

Pictures would be good for us following your adventure.

Yes, we are delighted to part-take in others suffering..

[Pancakes]

I know your kiding but He seems to be taking the prospect of a full build or gone motor way better than I would! Just helps me and others learn too, way better than words.

[Conquiztador]

True cause i replaced the spark plugs, not long ago well, roughly 300k ago, because the last time i had a problem, it was the plug on that cyclinder, and they are NGK BR9EIX iridium....$23 a plug....
I think its a hole in the piston aswell, from wat i can sence, but ill put some pics up when i start takin it apart... i will have to take the whole engine out of the bike anyways, ya?
any particular order to do it in?
usualy i work on cars, so hopefully bikes are simpler

If you can get head off without engine out then you be OK to chek her w/o taking engine out. Depends on frame and space. But if there is a hole then yes, out she comes and apart as you will have bits inside.

I know your kiding but He seems to be taking the prospect of a full build or gone motor way better than I would! Just helps me and others learn too, way better than words.

True. Just have learnt that what has happened has happened, so no use to get too depressed re it. And yes, he is doing well!!

Sure does sound like you have holed a piston.
I had frequent holed pistons when I raced 2 stroke Yams, the cure, after replacing piston and other damage, was to use 2 spark plug washers under each plug.
This moved the flame path of the ignition a little further away from the piston crown, no loss of performance but certainly cured the holed piston syndrome.

Good advice!! And remember, that plugs come in different thread lenghts too...

[Marls]

I hope you got the correct plugs. If you got ones that are too hot then you can burn a hole through the piston. If you got ones that are too cold you can sieze it too.

Let us know what the deal is when you get the head off. It could be so bad that it may not be worth even rebuilding it. Hard to say. Not sure about parts, yamaha shop will be able to source them I think but may be cheaper to buy from overseas.

ok, the plugs quoted from the JAPANEzy manual, says BR9ECM and mine are BR9EIX (as i just replaced wat was in there) and i cant realy judge the distance between the gap (dont have that tool, but the manual says .7mm - .8mm)

[Conquiztador]

Bike........................Year...........NGK.... ...Alternative.......Iridium
TZR 250 " V2".........1991-1995..BR9ECM....BR9ECMVX
TZR 250 (2MA)........1987-1989..BR9ES......BR9EVX..........BR9EIX
TZR 250R/RS/RSP....1993-.........BR9ECM....BR9ECMVX

You have a Iridium plug that is for the TZR 250 (2MA) 1987-1989. Apperently not recommended for any of the other TZR's. From the NGK website.

[Marls]

#$@#$
well.... cant do anyting now... ill just have to live n learn.... start the dismantling friday...me day off... expect some pics

[Marls]

ok, couldnt wait, so i took some pics, they ok, for my fone so....comon lets get some theories.... the top of the piston looks like it had somthing smashing it... i am just wondering if the other piston is in similiar condition now.

[Conquiztador]

Bummer...if there is no hole in the other one I owe Luka a beer...

A wild guess: Stretched conrod/damaged big end and piston hitting the head??

[Richard Mc F]

I should have put money on my original prediction..............looks bad........xt660 conversion any one ?

[imdying]

Just rebuild that motor.

[Ixion]

Bummer...if there is no hole in the other one I owe Luka a beer...

A wild guess: Stretched conrod/damaged big end and piston hitting the head??

Not entirely. The piston skirt may have collapsed, can't tell until the barrel is off. Somethings taken out the compression. Either a piston's gone or a big end is badly run.

EDIT: If the big end is gone, the conrod doesn't need to be stretched, just the play in the big end will allow the piston to rise too high in the cylinder, thrown upward by the other cylinder and inertia.