To Bore or not to Bore

My '98 WR400 has low compression.

I am considering just honing the cylinder and replacing the rings.

I figure I could save a little $$$ I just don't want to end up 50 miles into the back country and have it lay down on me. :)

Any suggestions?

My '98 WR400 has low compression.

I am considering just honing the cylinder and replacing the rings.

I figure I could save a little $$$ I just don't want to end up 50 miles into the back country and have it lay down on me. :)

Any suggestions?

Measure it, if its all square (vertical) and round (horizontal) then hone and re-ring it. If its questionable, bore it. Dont go anymore than needed to clean it all up.

hi,

can we put in a 426 or 450 piston inside a 98wr400

motor?

thanks. :)

If the nicasil is intact and the bore is dimmensionally within spec, then US Chrome suggests deglazing by using a Scotchbrite 7447 handpad, by hand of course.

Replating is the only option if your bore surface is out of tolerance.

Low compression could also be a signal of your valve/valve seat condition, in fact I would suspect this first.

An qualified cylinder head shop can inspect and repair this for you, I would tend to find a motorcycle specific machine shop though.

To make a 400 a 426 requires a rebore and replate.

To make a 400 a 444 requires a 426 rod and cylinder as the small end size is larger on the 426 and the 400 barrel does not have the required meat to bore to a 97mm.

jasowiii

Making sure the cylander is not out of spec would be the best way to determine that one. Only way to do that is to have the cylander measured per spec by a machine shop that can do it, Unless you have a dial indicator that can do this.

I would say that if the cylander is in spec yes possibly a new set of rings will help. But and here is the big but.

Since it is a 98 400 I assume you have some good milage on it. If you plan to keep the bike then get a new top end. If you want to sell it. put rings on it and sell it.

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