Boreing a RM85

K

kstarr87

Member

Jul 6, 2002

34

0

• Jan 30, 2003

• #1

Hi i have a 2002 rm85 and i want to bore it out. I can do it in my votech class but is there anything i should know before i do it like what i need? I want to bore it to atleast 100cc.
Thanks Kevin

 

M

MikeS

LIFETIME SPONSOR

Jun 12, 2000

716

1

• Jan 30, 2003

• #2

The 02 is plated.

Boring can be done at your school but you will need the specs, details on port chamfering and someone to replate the cylinder and then properly hone the plating to spec.

 

K

kstarr87

Member

Jul 6, 2002

34

0

• Jan 31, 2003

• Thread starter
• #3

Do you think it is worth it? Do you know what kind of power gain it will get? Kids in my votech class say it will bairley make a difference.

 

C

cr25096er

Member

Apr 16, 2002

707

0

• Jan 31, 2003

• #4

its a waste of time n money. send it to eg if u want more power.

 

K

kstarr87

Member

Jul 6, 2002

34

0

• Jan 31, 2003

• Thread starter
• #5

Kids in my tech class say that when you bore it out it bairley makes a difference. Is that true?

 

Jasle

Sponsoring Member

Nov 27, 2001

1,358

0

• Jan 31, 2003

• #6

Not true! Its a pretty huge difference. Tough to do in your votech class unless you have the capability to do the coating yourself. Not many places do nikasil coating. You can send your cylinder off to millenium for under $200 for bore and coat. Eric gorr can bore, coat, and port for slightly more. Rebuilding you motor is worth it in the votech class but the actual boreing is best left to the pro's unless you really want to learn how!

 

M

MikeS

LIFETIME SPONSOR

Jun 12, 2000

716

1

• Jan 31, 2003

• #7

I have an 03 that Eric Gorr did for me. 102 cc using a YZ 105 piston.

I had it dynoed, Jetting was not dialed in or anything else. We just threw it together ran it. HP varied from 19.4 - 20.7 (we had some issues with the tire we had on the rear :( ) Stock is somewhere around 18. Top end goes flat but tons of low end and a killer mid range.

This project I would not recommend for school. You can call Eric Gorr (see the link to the left) I am sure he would be happy to guide you or your teacher through the basics provided you have a spare cylinder around just incase :)

Goodluck

 

K

kstarr87

Member

Jul 6, 2002

34

0

• Feb 1, 2003

• Thread starter
• #8

I think i will call Eric and have him do it for me. Does anyone know of anyother thing i can get/do to it for more power? I already have a FMF Fatty and Power Core2 silencer.
Thanks for all the help!

 

nikki

Moto Junkie

Apr 21, 2000

5,802

1

• Feb 3, 2003

• #9

Another option may be to buy a 105cc cylinder and piston kit. Not sure if the '03 RM 105cc cylinder would bolt right up or not, though. I would be careful if you bore it yourself, if you don't get it in the right specs, a new cylinder, head, piston, rod, crank, etc. can get very expensive.

I have a few friends who are running 105cc's on their 85's in the supermini and womens 12-15 class and they all like the power gain and say it's noticable.

For more power... away from porting/boring and exhaust - maybe try a V-force reed cage and/or change the gearing.

 

M

MikeS

LIFETIME SPONSOR

Jun 12, 2000

716

1

• Feb 3, 2003

• #10

Junior spent 4 hours riding some challenging Pennsylvania terrian yesterday with his RM100 that Eric did. I finally jetted it for the 44 degree temps. He said the bike has more than enough power. He looped out 3 times in sections he though was not possible (the 3 other riders where in aw.)

Drag races with another KX100 and KX125(99) were only limited to traction, no sure winner (Junior is 40lbs heavier than the other 2 pilots.) When Bikes were swapped the Yellow was out front more often. The KX100 rider commented the RM was real....fast :)

We are running a DOMA exhaust and a V force set on the High setting, MR2 fuel (Xamax oil 20:1), 1 up on main, 1 down on pilot, clip #3, Timing is retarded some.

Good luck on your adventure with big bores!!

 

Last edited: Feb 3, 2003

K

kstarr87

Member

Jul 6, 2002

34

0

• Feb 3, 2003

• Thread starter
• #11

Nikki where can i get the 105cc cylinder and piston kits at?

 

M

MikeS

LIFETIME SPONSOR

Jun 12, 2000

716

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• Feb 3, 2003

• #12

Kstarr

The EG 105 kit does not bolt on without case mods. The 99cc wiesco kit does but may have some reliability issues (not sure). Eric also modifies the cylinder for your type of power.

 

B

Brianc

Member

Nov 14, 2001

138

0

• Feb 3, 2003

• #13

I read somewhere in a thread that the 85's are already oversquare and the real power gain was reached thru stroking the crank. Ask Eric about that, it could be less expensive and provide more usable power.

 

K

kstarr87

Member

Jul 6, 2002

34

0

• Feb 3, 2003

• Thread starter
• #14

MikeS where can i get the 99cc wiseco kit?

 

K

ktmdad

Member

Feb 29, 2000

314

0

• Feb 4, 2003

• #15

Any dealer that sells Wiseco can get you the pistons.

 

M

MikeS

LIFETIME SPONSOR

Jun 12, 2000

716

1

• Feb 4, 2003

• #16

Thanks 'dad :)


PS The stroking (3.2mm) used by a few tuners with the .80 over kit does yield a potent motor. Power is like stock...just 2 notches higher everywhere. Mid to top power is enhanced. The over Square kit that EG produces seems to be the best for the $$$ IMO