OYL's Mini Roadracers Forum

[MOTOHEAD52]

Matt and Steve have made some very good points on your repair, but I think Teddy has made the most important one. Keep it relatively stock and reliable and get in the laps. Stock dirt bike motors are already in a fairly high state of tune and should give you a good bang for your buck. To that end I would price a new stock cylinder and head along with all the other parts you are going to need. There appears to be a spot on your cylinder that may need repaired. If the damage is beyond the size a stock or "B" overbore will require, it would have to be welded before it is rebored, stripped and replated. Personally, I would not put that much $ in a used welded cylinder. Send it to millenium for appraisal. They can get a new stock kaw or wiseco piston of the correct size once they have cleaned up the cylinder. They can get them just as cheap as you. Remember, you are only allowed up to .5mm overbore or you have a F1 motor. Getting your head recut is expensive and may also cause other problems. A stock head keeps it simple and may be cheaper.
Just my opinion.

You are too damn fast already, don't listen to any of this. Build a grenade and blow up often

[lucky13]

Being a member of the Steve, Teddy, and Bil mutual-admiration society, I agree completely. I would never tell somebody else what kind of bike they should run and I'm all for high-performance engines but when it comes to mini-racing I don't quite get the horsepower race and I'm much more in favor of stock machines, maximum track time, learning to go faster, few if any mechanical dnf's, best rider wins. But, who cares what I think?

[Steve-o]

But, who cares what I think?

I think we all know the answer to that one matt...

[lucky13]

But, who cares what I think?

I think we all know the answer to that one matt...

[Luckystar64]

It looks like you do need a top end on that bike-- but! I had a problem with my Metrakit when it was low on gas. When I turned to the left... all the gas sloshed to the left, and it acted like it ran out of gas until it was upright.

The jetting probably is a little rich too. I'd do the top end first and then try it out. ---L*64

[groundrules]

:!: get new crank bearings, rod as it looks like it is smoked...

As someone who's been inside these things only a little bit, I'm still learning some of the visual diagnosis skills. Question for ya: is there something you see in the photos that would lead you say specifically that the rod is shot, or are you just assuming since the rest of the top end is done, it's probably rod time too? thanks!

[teddy]

IF your motor has had that much blow by it might have affected the crank and rod bearing surfaces? You know excess heat from combustion.... limited oil vapor..........

I have no idea what pre-mix oil you have used or the previous owner, or what mix ratio...... I run 32:1, Klotz BENOL........ or sometimes spent big money on fancy Motul Race oil.......... OIL is KEY

If the rod does not tilt side to side AT ALL it might be fine for the season......... then again maybe not......

As long as the motor is apart press in new crank bearings at the minimum. Have one of your "bro OLYers" inspect your motor as there are a few of them that should know how to check out your motors crank

[Alexchannell]

Well I got my cylinder back from millenium on friday, but they used a griding on one of the ports and scratched the bore. Unacceptable. Calling today to get an RA number.

[teddy]

Really................ that is very very ODD

I can't imagine them sending it to you like that?...........

[lucky13]

Well I got my cylinder back from millenium on friday, but they used a griding on one of the ports and scratched the bore. Unacceptable. Calling today to get an RA number.

Take a pic before you send it back.

[teddy]

I'm not quite sure what you mean by "griding", a photo is in order......... post it up.

[Alexchannell]

I'm not quite sure what you mean by "griding", a photo is in order......... post it up.

Whoops....grinding...

[teddy]

You talking about that little smear/chuff/scratch above the left intake port? Or between the ports?

What did they say about the marks you are questioning?

I would certainly want to now what they had to say prior to building the motor and trust them

[lucky13]

It is hard to tell how deep the marks are in the picture or if they have any little burrs that could mark the piston or ring but here's how I think I'd feel about it....I'll bet that the marks are small enough and not deep enough to really have an impact but I'd be really disappointed that I paid a bunch of money and that what I got was in some way flawed. I think I'd send it back too and I'll bet that a re-hone would take care of it.

Don't take only my word, though. I've never had this kind of experience personally so maybe someone who has had this kind of thing happen can be a bit more specific and helpful.

[Alexchannell]

Both areas are spots of concern.

I can't think of any reason why they would grind the area between the ports, any ideas?
The small scuff mark I really don't like, you can feel it with a finger, especially if you use your nail.
I am email that picture to them and awaiting a response.

Yeah the areas probably wouldn't hurt anything, but it should be perfect.

[JRoot]

Anybody know why they ground relief on the web between the exhaust ports?
Not questioning the job they did, just looking for the logic behind it.

[MOTOHEAD52]

Stock two stroke cylinders that have a "bridge" between the ports are recessed in that area from the factory. If you had the cylinder bored larger then stock they would also have to put that recess back in the port area. I've always thought the reason was to cut down on the heat generated in an already thin, hot area.

[lucky13]

Stock two stroke cylinders that have a "bridge" between the ports are recessed in that area from the factory.

I think the bridge between exhaust ports is recessed because you get a big concentration of heat in that area and the web/bridge is prone to expansion into the cylinder if you don't do something. I THINK that's why but I might have also had a dream about this and could be totally full of crap so go easy on me if I've said something stupid.

[lucky13]

Looks like we came to the same conclusion at the same time, Bill. That makes it unanimous and nobody else is awake so that's our final answer.

[Hundo811]

Looks like we came to the same conclusion at the same time, Bill.

Actually it looks like Bill beat you by 13 minutes.