Quick questions about rebuilding '01 426


7 replies to this topic
  • DrThumper

Posted November 17, 2006 - 09:14 AM

#1

I'm about ready to start doing a top-end on my '01 426. I have rebuild a few motors in the past, but this is my first hi-end 4 stroke, so I got a few questions as I prepare to make a cost estimate (for the wife's approval, of course).

I'm going to replace the piston, rings, wrist pin, cam chain, valve seals and do a valve adjust (did I leave anything out?). When I open up the cylinder, if I find it scored, or out of spec, what is the common fix? Re-sleeve or bore out (and install an oversize piston, as in cars)? If a bore can be done, do they sell oversize pistons (I haven't seen any on the internet), and will a common machine shop do it? Cost estimate of a bore? Cost of re-sleeve?

Thanks guys
p.s. Any tricks, hints?

  • Birdy426

Posted November 17, 2006 - 09:44 AM

#2

Mic the valve guides as well, and carefully inspect the valves, esp for tuliping at the outer edges and cracks at the stem. If you have to replace the valves, they are about 60 bucks each. Be sure you have the seats cut if you replace valves, or the new ones will wear really quickly. Oh, and in spite of what the book says, don't lap Titanium valves, as it removes the hard coating on the wear surfaces. I would also replace the springs (they are cheap from Yamaha, and failure, while uncommon, is really catastrophic). Check the big end of the rod for slop, and mic the small end as well while you have things apart. Piston kit is about a benjamin, valve springs are about 30 bucks, seals are about 20 bucks, and gaskets will be another 40 or so. I would replace the cam chain tensioner as well. If you haven't already done it, now is a great time to install an autodecomp cam (about 100 bucks), either from an 03 or newer 450 or hot cams. I have the hot cams version in my 444 and love it. Valve shims are about 5 bucks each, but some dealers will swap 1 for 1 if you bring in your old ones. It never hurts to ask. The TT store is the cheapest place to buy your parts. Plan ahead and order everything at once, as the OEM side of the house ships a little slower than the after market side.

As far as the bore, there are a couple of options. If it's worn or scored, you can either sleeve it (LA Sleeve, I have no experience doing this), or send it off to someone like Luke's racing or Eric Gorr's forward motion to have it stripped and replated. They can weld up any scores as well. Price depends on how much work they have to do. Another option is a big bore kit, again from either Lukes or Gorr. I've used both of these shops before (Gorr for big bore kits, replating, valve jobs and porting, and Luke's for Big Bore kits when Eric didn't have what I needed in stock and I needed it in a hurry). Both are first rate and turn out great product. The 444 kit for my 01 WR was about 450 smackers, and the cost was a push compared to stripping and replating my worn cylinder and getting a wiseco hi comp piston kit. Kit comes with all the gaskets and everything else you need. Remember, there’s no replacement for displacement, and as long as you gotta spend the bank anyway, go big or go home.

I went thru my entire motor last winter, all new bearings, new crank, big bore, cams, clutch, valves, seats, springs, port work, hot cams etc, and spent about 1500 bucks all up. It should be good for another 5 or 6 years with regular oil changes, and makes more power than I will ever need.

If you have more questions, feel free to PM me.

  • DrThumper

Posted November 17, 2006 - 09:58 AM

#3

Thanks Birdy! You get a fuel tank for that!
My valves are steel and I want to keep them that way. I have some freinds with Ti valves and are constantly having to adjust them. I adjusted my when the bike was 1 yr old, checked them twice a year since, and just now they need another adjust...maybe replace upon veiwing (thanks to your input, Birdy). I'm not too intersted in a 444 kit, just because I don't race anymore and I plan to get a new bike in 2 years (or sooner) depending on my budget after I get a new sled next year. Thanks for the names/places to send the cylinder (if needed). Since it just started snowing up here, I got time, I plan to open her up, do all the inspection and buy what I need. Of course, TT Store gets the first shot!

  • idahoaggie99

Posted November 17, 2006 - 11:06 AM

#4

[quote name='DrThumper']I'm about ready to start doing a top-end on my '01 426.
QUOTE]

What indicator did you use to determine that it was time for a top end rebuild?

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  • DrThumper

Posted November 17, 2006 - 12:17 PM

#5

[quote name='idahoaggie99'][quote name='DrThumper']I'm about ready to start doing a top-end on my '01 426.
QUOTE]

What indicator did you use to determine that it was time for a top end rebuild?[/QUOTE]

Boredom, its winter up here....LOL....I got about 5 yrs of hard riding on it, valves due for adjust and have a slight noise (probably stretched cam chain). I want this bike to run strong for about 2 more years and still be worth something when I sell it. Also preventative maintenance, I do a lot of riding out in the middle of nowhere (Moab, North Utah, Idaho, etc) and do not want to have a major breakdown...and lastly, money burning a hole in my pocket.:cheers:

  • Birdy426

Posted November 17, 2006 - 02:49 PM

#6

Thanks Birdy! You get a fuel tank for that!
My valves are steel and I want to keep them that way. I have some freinds with Ti valves and are constantly having to adjust them. I adjusted my when the bike was 1 yr old, checked them twice a year since, and just now they need another adjust...maybe replace upon veiwing (thanks to your input, Birdy). I'm not too intersted in a 444 kit, just because I don't race anymore and I plan to get a new bike in 2 years (or sooner) depending on my budget after I get a new sled next year. Thanks for the names/places to send the cylinder (if needed). Since it just started snowing up here, I got time, I plan to open her up, do all the inspection and buy what I need. Of course, TT Store gets the first shot!


Did the steel valves come stock in your 01? Mine has Ti...good on ya, they should last forever and a day. As far as the 444 kit, I know what you mean. I'm not a racer either. I only did mine cuz the cylinder was worn out of limits, it was about a push cost-wise, Luke's had the kit on the shelf, and I was in a bit of a hurry to get it back together (it would have taken a couple of weeks to get the stock bore redone). When you get a new piston kit, both the Wiseco and JE forged pistons run a little looser than stock, so they are a bit noisier. Also, when I had the stock bore and a 13.5:1 Wiseco, pump premium worked fine in all conditions. Going to the big bore with 13.5:1, I have to run race gas to keep the death rattle at bay.


Thanks for the fuel!

  • Oasis_Flame

Posted November 18, 2006 - 09:01 AM

#7

Dr T
I too run the Wiseco 13.5to1 piston with no ping or heating problems on pump gas. Makes very good power in all rpm's. I'd stay with steel valves as well, mine costed $28.00 a piece. New seals and guides would smart at this rebuild time.

  • DrThumper

Posted November 20, 2006 - 08:48 AM

#8

Did the steel valves come stock in your 01? Mine has Ti...

Thanks for the fuel!


Oops, my mistake, its a 2000. Too many toys in the fleet, hard to keep track. Its also a YZ, I guess I posted in the wrong forum....man, I'm just having one of those days....:cheers:




 
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