67mm risky bore??

[200xkwit]

I ordered the 67mm pistion for my new top end I have to do on my 3wheeler and the guy at the locla honda dealer kept asking me if I was sure if I wanted to bore that much and that it was risky and that its really thin yata yata yata this is spossed to be the high compression 12;1 piston I :eek: got here. but the dealer guy has me thinking twice... should I be worried?

[KASEY]

I WOULD NEVER,,,,,, bore an engine more than it needs to clean up,,,, thats just wasteful ,,,,and costly..... there is NOT enough cc difference to make a difference in power,,,, and if something goes wrong................ your buying a cylinder not just a bore job..... and the place where i have my work done will charge double to bore a cylinder that much,,,, oh did i say i think its a bad idea????? then i will,,,, its a bad idea,,,,,,,,

[200xkwit]

well its already bored im just sayin its till reliable right?

[TimSr]

The thinner the sleeve, the more likely for the sleeve skirt to break or bend (its not pretty when they break) and the less efficiently it will dissipate heat to cool. Not necessarily unreliable, but not AS reliable, on top of everything Kasey said which I agree with 100%. Boring is for fixing worn out cylinders. It is NOT a performance modification. I hope your bore was shot before you did it, and you didnt just waste all the good metal off the sleeve expecting it to enhance performance.

[200xkwit]

yea it was shot really bad I had sezied a piston in there before. but isnt there alot of ppl on here that have a 12:1 compression piston in thee 200xes?

[kilabeez0]

ask vartiak what happened to his :o

[83185s]

jusyt cause its a 12:1 doesnt mean that u have the biggest bore..u can get a smaller 12:1 than the 67mm..thats the max..trailprotrailpro screwed if it screws up again..i have it done on my 185 with the 200x top end tho so were on the same track..but i also have a spare 185 cylinder with piston incase..also..did u happen to get a high strength cam chain? if not its gonna break really soon after u put that in..i went out and bought all new cam stuff with that piston to be on the safe side..if trailprotrailpro just putting that piston on..have fun with the fixing..if u bought high strength cam chain and new guide and tensioner then u should be ok for awhile..i wouldnt have done it if i was u unless i had to..IMO

[KASEY]

i also hope your kicker gear train is all good or you will be replacing parts soon enough,,,,,,,,,,,

[deathman53]

why are you guys buying a 12:1 piston, do you like using race gas? Its about $6 a gallon here. My crf450r and ac250r uses race gas(track bikes only), my 200x and xr250r have 10.25:1 pistons, they use pump gas. I'd go broke if my xr250r used race gas. With being on the track you don't burn as much gas as you would trail riding(for the simple fact that most of the time trail rides end up at nearly 40 miles(atleast me). Also track riding you have more down time, trail riding(well atleast for me) is constant riding. I'd strongly consider a 10.25:1 pistonif I were you. $6 a gallon gets expensive fast.

[HaggLE]

Ive seen bigger in 185/200 cylinders. By going to the biggest bore size for the cylinder how it currently is doesnt mean its the end of the world. 2 strokes are another story. 4 strokes dont have complications like 2 strokes do with port timings. Ive seen upto 70mm in one of these. You do have to press in a new sleeve but it isnt that bigger deal with 4 strokes. It isnt the end of the world.

[short4stuff]

Ive seen bigger in 185/200 cylinders. By going to the biggest bore size for the cylinder how it currently is doesnt mean its the end of the world. 2 strokes are another story. 4 strokes dont have complications like 2 strokes do with port timings. Ive seen upto 70mm in one of these. You do have to press in a new sleeve but it isnt that bigger deal with 4 strokes. It isnt the end of the world.

where do you get the bigger sleeve/piston ? .... Or what does it come from (what other model of bike/trike..)

[83185s]

thats what i wanna know..and do u got a pic of any of it?..

[short4stuff]

HaggLE - can you tell us about the larger sleeve/piston set-up ?!!!

[Oldshell4481]

alright, i dont no much about this kinda stuff, but what is the need to bore a cylinder? my 3 wheeler is fine, and i dont think the cylinders have ever been touched.

[short4stuff]

alright, i dont no much about this kinda stuff, but what is the need to bore a cylinder? my 3 wheeler is fine, and i dont think the cylinders have ever been touched.

well the cylinders wear .. become out of round and such things... the clearence between the piston and cylinder is suppose to be like .002 -.004" .. now think about that .. thats like the thickness of a piece of paper... things wear causing compression lose, which means a lose of power.

I just thought of something ..

83185s ... did you get an oversized head gasket? .. I have my 185 cylinder bored to a 65mm .. and i think if i went to a 66mm that the head gasket would probably be partially in the cylinder, I couldnt imagine with a 67mm bore.

[HaggLE]

You can get a sleeve from any other bike/trike (4 stroke that is) as long as the outer measurement of the skirt is about 73-74mm and the inner size (bore size) is smaller than 70mm. 4 cylinder bikes are the best to search for.
All you need to do now is machine out the old sleeve out and press in the new sleeve (done at a machine shop) and bore and hone to suit 70mm.

For the head gasket run a standard Honda TLR250 head gasket. It will fit straight in and is designed for a 70mm piston.

The piston to use is a TLR250 piston because as i previously said the bore size is 70mm. The only problem with the TLR250 piston is that it will sit lower down in the bore. To fix this you will have to have the bottom of the cylinder machined off to suit. Measure this with verniers after you have had the sleeve put in and sit it together without rings and with the head off and using a new base gasket. Make it sit down the bore about .030" to ensure that the compression isnt too high. You will need to run a new cam chain to compensate for the shorter cylinder.

The next step is you will have to machine out the hole that the skirt goes into in the cases. The bigger sleeve skirt wont fit in. A machine shop can do this also. Trim the base gasket to suit the bigger sleeve.

An alternative to changing the sleeve is to buy a complete TLR250 cylinder new from Honda and adjusting the length to suit. The bore will already be done and you will be machining the cylinder length either way.

Let me know if you have any further questions and ill try and get a picture for you.

[hondagrant]

Thats interesting i've heard people talking about taking them out to 70mm but i didnt know how it was done.Im runing a 67mm piston in my 200x but when it comes time for a rebuild I might consider that conversion...

[short4stuff]

hey .. what year is that tlr250 ? .. whats years were they made...
also is 70mm the max bore for that piston .. or can you get oversized? .. will the bottom end accept a larger piston than that..
you know incase it blows or .. yeah you need to bore ..

[Bigmikeyall]

I put a 66mm 12:1 skirted piston in the original stroker motor that came with my trike (it was an old race bike). I ported and polished the head and installed heavy duty valves and springs. I broke the bike in for about a month because I stuck so much money in it. Then one day later I was really on it going down my road the whole engine blew. When I say blew the crank case split in three areas and the jug cracked all the way up to the head. I stripped the engine down and couldn't even find something that resembled a piston. My advise to you is keep it simple. Don't go over anymore than you need to clean the cylinder. Be very worried........I like to think I built my motor the right way and it still took a crap.

[short4stuff]

HaggLE - do you know how much lower the tlr piston sits down compared to the stock piston?

Bigmikeyall = break it in the way your gonna drive it :welcome:

[leevarnado]

really old thread ,but has anyone done this.

[factoryX]

wait, so boring out a 250r to a 310 is a waste? am I missing something? or is this a 4 stroke only type deal?

[oscarmayer]

ok jsut for the record, you don't have to run race fuel with 12:1. if you proeprly tune it then 93 pump will run just fine. tuning is the key just like any other thing. I've seen well tuned stocker bikes out run tweaked bikes cause the knuckle head could not tune to save his life. learn to tune or find someone who can tune it. it'll not only make you more power, but also help it last way longer!

[leevarnado]

would like to if anyone has put the trl 250 head on a honda atc 200 engine .