whyzee

Never enough time !
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Dec 24, 2001
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I'm posting this here because I know Eric is about 8 weeks away from being able to answer this e-mail I just sent him, and I hope there is someone here whom has used his services and can provide ANY feedback. Thanks.

Hey Eric,

I’ve got a 96’ yz125 that I picked up about 4 months ago, it’s my first dirt 2 stroke and it looks like I am going to need to replace my top end. I got a NEW compression gauge, warmed up the motor for about 5 min. took plug out, gauge in, fuel off, throttle wide open, finger on the kill switch, kick about 7 or 8 times. I get a high reading of 122 psi., this does not sound good according to the DRN forum posts I have been reading. So I guess its new piston, rings, etc. The thing is, it feels like a rocket to me, I can't imagine the ride after the top end is replaced.

I would like to send you the cylinder and head to have you perform the ‘Low-Mid’ porting job. I do not race but it is something I would like to do in the future, maybe 6 months to 1 year from now. I understand you clean and re-set the exhaust valves in this price. Is there any reason I should have the big bore job done at the same time? I see this costs $375 ‘With Crankcase Mods’, do you have to modify the crankcase to do a big bore? Does this price include a new piston, ring, pin, circlips, bearing and gaskets kit at the same time? Does the $375.00 include the porting? I’m sure you get asked these questions all the time so I hope you know I appreciate your time.

To help in your evaluation here are my stats:
Stock exhaust
Stock main jet
Ride 2 hours per week, mostly moderate to hard throttle.
Yamalube 2-R @ 32:1.
BP racing 100 octane fuel uncut.
NGK BR8EG.
Boyesen pro series carbon fiber reeds, checked last week, still perfect.
Mikuni TMX36SS with 360 main jet and factory settings
FYI: I’m 40 yrs. 175 lbs. 5’-9” for what that is worth.

When I send everything in do I need to include the existing piston?

Thanks in advance,
Dave Peterson
DRN member: 96whyzee125

Also, will adding a future Pro-Circuit exhaust require a different porting?

I am also probably going to switch fuels to 007 Blue 112.25 octane leaded fuel cut 50/50 with 93 octane unleaded pump fuel and changing to oil to Maxima Super M after the top end is replaced(BP is not reliable with stocking their race fuel)…will this require a different porting?

And lastly, if I race AMA sanctioned races is the “Big Bore” going to disqualify the bike?

Thanks for any input
:eek:
 
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RM_guy

Moderator
Damn Yankees
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Nov 21, 2000
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122 psi is definitely too low. You will notice more power after the new top end especially more low end. Eric’s std port job will give you a smoother powerband and adjust the compression to match the race gas that you are using. Part of the porting is grinding the exhaust valve to match the port shape. He gives them a good cleaning while he’s at it. He will need the cylinder (with the PV in it) and the head.

The big bore job includes the porting, piston, rings and case mods (if you need them, I’m not sure if the YZ has enough clearance or not). I’m also not sure about gaskets. The std porting doesn’t include them but he can get them for you.

It’s up to you on the big bore kit. I know a lot of members have gotten it and enjoy the extra power. I’m sure there will be more opinions.

Good luck
 

Jammertime

Member
Dec 30, 2001
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I agree with RM_GUY. You will see a difference with a new top end. Eric can fix you up. Just print his order form and fill it out. I will add that a big bore kit is not AMA legal, but he can go 80 over, which is legal. I have used his services and am well pleased! He was very quick to e-mail me back when I needed help!
 

whyzee

Never enough time !
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Dec 24, 2001
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Thanks RM and Jammer,

I think filling out the order form should be the easy part.
I'm sorry, maybe I should have phrased my questions better:

When Eric refers to ‘case mods’, is he talking about needing the engine case to work on or modifications to the cylinder at the case connection area?

Am I looking at the correct porting job, or should I be thinking about the ‘Mo-better everywhere?

Will changing fuels require an adjustment to the porting?

Will changing the pipe and silencer require an adjustment to the porting?

Eric offers an AMA overbore kit, is there any significant power gain over stock, and does this include the porting job?

Will continuing to ride the bike untill i get the top end done cause more harm?

Thanks again for any input,
Dave

FYI: even at this low psi the bike never fouls plugs and starts on first or second kick.:eek:
 
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whyzee

Never enough time !
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Dec 24, 2001
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Ok, so I just finished tearing down the bike, one hour max, and that includes stopping to wash my hands every five minutes to take pictures with the digital camera.

If someone has a site that would host the pictures or if you want to see any, I don't mind sending them.

Here’s what I see that concerns me:
The piston has a carbon build-up on the top, next to the front edge, about the size of a quarter.
The ring has a flat spot at the front edge where it looks like it has worn against the bridge and exhaust port area.
The cylinder has a very slight gouge on the edge of the exhaust bridge, but I can still see diagonal hone marks on the rest of the cylinder, mater of fact the rest of the cylinder looks perfect.
The piston even has the micro fine horizontal lines on it, as though it is fairly new?!
I’m sending the head, cylinder and piston to Eric tomorrow morning, I spoke with him today before I tore everything down.

Going with the AMA over bore, which includes the porting of my choice…Even though I would prefer the low end power now, in six months my riding level should benefit from the mid to upper band, so I’ll go with the ‘Mo-better everywhere’ job.

Eric did say that fuels have little to nothing to do with porting and an aftermarket pipe and silencer do not require any adjustments for porting.

While I’m waiting I think I’ll replace the clutch, chain, rollers and slide, and do the forks as well. Anyone have experience with having the rear shock re-charged?
Also, any ideas, thoughts on re-jetting with the new set-up?, currently have a 360 main.
:eek:
 
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'00kx250spode

Member
Oct 21, 2000
197
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You should call Eric and find out if he needs the bottom end. I don't think he will - but you want to be sure. If he doesn't need it, there's no need to remove and send the entire engine - just send the cylinder and head. If you include the piston and sparkplug, Eric will let you know if there's any problems with your jetting or leaks, etc.
 

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