Anyone get vibration with Wiseco XR280 kit.

[TobyS]

Anyone get vibration with Wiseco XR280 kit?

I haven't put the bike together yet, but I notice the piston and pin weigh 35g more than stock. Has anyone noticed an increase in vibration when they put in the 77mm piston? Should I try to get some weight off the piston, or would I be wasting my time?
Thanks in advance,
Toby S

 

[ACS]

A friend has a XR 280 and I rode it before and after the big bore. I didnt notice any vibration difference. The difference is that the 280 makes the bike about 50% better to ride.:)

 

[mtngoat]

That's a pretty astute observation, which would concern me too. I'd call WiseCo or White Bros tech dept. at (714) 692 3404

 

[TobyS]

I called them, and they said "it's within tolerance", which begs the question: whose tolerance? I didn't bother to ask, but I'll bet my paycheck that it's not within Honda's tolerances.
Honda did a great job of making their casting light, and this piston is bigger. Forging a piston requires more meat between the pin bores and the crown also. The pin is longer, which makes it 6g heavier, and I'm definitely not taking any material off that.
The counter balancer must still compensate well. I know that the bigger pistons (300 cc) must be even heavier, and I haven't heard any complaints from anyone.

 

[mtngoat]

I have a 96 and 98 XR4. The 96 has the 440 kit and I don't notice any vibration difference between the bikes.

I'm with you though. I would have expected factory balance tolerances to be maintained, absent which (to some degree I don't know) engine/bearing wear gets compromised.

Maybe it's not enough to cause a problem:think

 

[John K]

A friend of mine that has built plenty of XR's swears on
lightening and drilling pistons, IF done right!!! He did
this in his 280 but it wasn't a wiseco, I've heard they
have a tendancy to grab if the cylinder isn't machined
"right" for them, and if not run in correctly.

There is a picture of a 280 he had (late 80's model)
http://www.justxr.com/net_bikes/revs280.html

I could probably ask him for you if nobody else comes
forward with the info you are after.

 

[buckslayer]

Have any of you guys who run the 280cc kits noticed a difference in how quickly the engine revs, or where it makes the most power compared to stock?

John K - your friend willing to share how to lighten a piston correctly?

 

[DualSportr]

I know that the bigger pistons (300 cc) must be even heavier, and I haven't heard any complaints from anyone.

Nope, because if you use a more expensive piston, such as JE, Ross, or Arias, the weight is about the same as stock or slightly lighter.

Wiseco is a cheaper piston, they don't go through as much to get the weight correct as the piston companies mentioned above. Also, because the material is more flexible than higher quality pistons, Wiseco must have more internal bossing and framework.

Compare the Wiseco 77mm piston to a JE piston of the same size, you'll see the reason the JE piston costs about $50 more.

 

[TobyS]

Guru points for DualSportr

Stock Piston: 208g (measured)
Wiseco Piston: 237g (measured)
Ross Piston: 215g (claimed)
JE piston: 215g (claimed)
Pin weight is not included. The Wiseco pin was 6g heavier than stock, but it is longer, and the others may be as well.
One seller of Wiseco pistons said "you will get a little more vibration at high revs".
I'm going with Ross, because their guy (Jim) seemed most knowlegable. Look for an opportunity to buy an unused Wiseco piston on ebay soon.

 

[DualSportr]

I'm going with Ross, because their guy (Jim) seemed most knowlegable

Honda Jim at Ross is a way-cool guy. He's been in the biz for a looooong time, and knows his stuff.

 

[TexKDX]

I have been told the JB piston is the way to go. Per White Bros and Gary Hazel at Thumper, the vibration difference will be minimal and not due to the piston weight, rather due to the increased power provided with each explosion.

A friend of a friend did some major mods to an XR250. He tried basically everything but stroking it. In the end, he says to stay with the stock cam and stock carb, but get the plate that allows you to change the cam timing. It made the biggest difference of all the mods besides the bore. The cam just moved things around but created too much compromise, and he never could get the carb to work well.

Gary Hazel said the hot cams create reliability and durability problems thru follower wear, seat wear, and valve stretch.