Big bore for a 400... Which one???


18 replies to this topic
  • TallBoysWRF

Posted January 22, 2005 - 09:22 PM

#1

What big bore kits have you guys gone with and why did you choose that one. I need to replace the crank rod on my 99 WR400 and I am thinking about 'upgrading' the cc's while I am at it.

  • Dan_Lorenze

Posted January 22, 2005 - 09:30 PM

#2

Personally, I've never been a fan of big bore kits. I just don't think the bottom end would hold up bigger displacement over time. Engineers spend countless hours developing these engines to run their best with the stock specs. If you're looking for more power you might consider selling the bike and upgrading to a 450.. Just my thoughts...

Dan

  • Hamish

Posted January 22, 2005 - 11:44 PM

#3

frostbite just fitted a 430 to his 400, so he's the guy to ask.
As far as pistons go, JE is my preference.

  • Frostbite

Posted January 23, 2005 - 09:38 AM

#4

frostbite just fitted a 430 to his 400, so he's the guy to ask.
As far as pistons go, JE is my preference.


I just put it together last weekend but haven't been able to ride it yet. My countershaft seal tore and it's leaking badly so I'm stuck until the new one, (and 1 spare) arrive in the mail.
I got the kit from Thumper Racing in Texas. I sent them my barrel and they pushed out the old sleeve, bored the casing and installed a new sleeve. they also supply new piston, rings, wristpin, circlips, bigger jets and head, base and cam tensioner gaskets. There is no taper left in the bottom of the cylinder so you can't just slip in the piston like the stocker. A ring compressor is an absolute must! I spent hours trying to get the oil ring in without one and it is impossible. :cry:
The compression ratio stay s the same at 12.5:1 and it didn't feel any harder to kick over, although the new rings aren't broken in yet. It fired right up and ran smoothly but I shut it down after a minute due to the oil leak and the fact that Hotcams stresses that you should keep the RPM above 3000 for 1/2 hour for break in.
I'll put up a post once I get some miles on it. If the con rod's gonna break then riding at -40 slogging full throttle through 8 inches of snow every day should speed up the process. :cry:

  • Hamish

Posted January 23, 2005 - 12:18 PM

#5

There is no taper left in the bottom of the cylinder so you can't just slip in the piston like the stocker. A ring compressor is an absolute must! I spent hours trying to get the oil ring in without one and it is impossible. :cry:


2 small flat blade screwdrivers do the trick. You wanna try doing a 4 cyl engine :cry:

  • Frostbite

Posted January 23, 2005 - 02:25 PM

#6

2 small flat blade screwdrivers do the trick. You wanna try doing a 4 cyl engine :cry:


Hamish, no disrespect intended but GI Joe with the Kung Fu grip couldn't get that 430 oil ring in by hand. I was a mechanic at a Honda dealership for years, put lots of 4 cyls together including my own by hand no problem but that oil ring is one strange animal.
All of the 430 kit rings feel like they have a lot more tension than the stock rings. Without the taper at the bottom of the cylinder it's tricky but not too bad to get the first 2 rings in but the fun stops there. My stock piston would slip in the original bore easily. The 430 oil ring packaging even states that a ring compressor must be used. Of course I didn't believe it at first.
2 screwdrivers? I had 6 feeler strips trying to shoe horn :cry: that sucker in with the 1st 2 rings already in the bore. I'd get it halfway in and the spacer would overlap or the bottom retainer ring would pop out of the groove.
If you've put one in by hand, brother you've got skills, and the patience of Jobe! :cry: :cry: :cry:

  • TallBoysWRF

Posted January 23, 2005 - 02:40 PM

#7

Frostbite, How much of a wall was left after your cylinder was redone? You say there was no taper left, but how much wall was left entact?

  • Frostbite

Posted January 23, 2005 - 03:00 PM

#8

Frostbite, How much of a wall was left after your cylinder was redone? You say there was no taper left, but how much wall was left entact?


Thumper Racing removes the original sleeve, bores the cylinder casting and then presses in an oversized sleeve so I assume the sleeve is as thick as it needs to be. It just doesn't have a taper like the stocker.
A compressor is not a big deal unless the closest one is 1000 miles away. I made one out of a fence post clamp.

  • Hamish

Posted January 24, 2005 - 03:54 AM

#9

Hamish, no disrespect intended but GI Joe with the Kung Fu grip couldn't get that 430 oil ring in by hand. I was a mechanic at a Honda dealership for years, put lots of 4 cyls together including my own by hand no problem but that oil ring is one strange animal.


Hmm...a tough one hey.. I'm yet to come across a piston I couldnt install by hand, but there's a first time for everything.

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  • TallBoysWRF

Posted January 24, 2005 - 05:18 PM

#10

Has anyone just bolted a 426 cylinder on with a 426 piston and rod?

  • SXP

Posted January 24, 2005 - 09:11 PM

#11

Has anyone just bolted a 426 cylinder on with a 426 piston and rod?


I went both routes. I started out with the Thumper Racing 430 kit using my original cylinder which was sleeved as Frostbite explained (BTW, I had no problems with the oil ring :cry: ) with their "special" 95 mm Wiseco piston which uses the stock 18 mm wrist pin. The iron sleeved cylinder is one heavy mutha! I ran the bike this way for a while. I then decided to rebuild the stock crank with the 426 rod (19 mm wrist pin) and sent it off to Eric Gorr. While perusing his web site I noticed he was blowing out bored out (to 95 mm) and Nikasil plated cylinders for $100 (no exchange needed) and grabbed one. I already had a 95 mm Wiseco piston with the 19 mm wrist pin so that's what I ended up with in my bike - rebuilt crank/bearing with a 426 rod, bored out nikasil coated cylinder and 95 mm Wiseco piston. Time to send the head to Eric Gorr for a rebuid - expensive hobby!

BTW, as far as reliabilty goes I have about 3500 miles on the rebuild with no problems.

  • Frostbite

Posted January 25, 2005 - 07:37 AM

#12

I went both routes. I started out with the Thumper Racing 430 kit using my original cylinder which was sleeved as Frostbite explained (BTW, I had no problems with the oil ring :cry: ) with their "special" 95 mm Wiseco piston which uses the stock 18 mm wrist pin. The iron sleeved cylinder is one heavy mutha! I ran the bike this way for a while. I then decided to rebuild the stock crank with the 426 rod (19 mm wrist pin) and sent it off to Eric Gorr. While perusing his web site I noticed he was blowing out bored out (to 95 mm) and Nikasil plated cylinders for $100 (no exchange needed) and grabbed one. I already had a 95 mm Wiseco piston with the 19 mm wrist pin so that's what I ended up with in my bike - rebuilt crank/bearing with a 426 rod, bored out nikasil coated cylinder and 95 mm Wiseco piston. Time to send the head to Eric Gorr for a rebuid - expensive hobby!

BTW, as far as reliabilty goes I have about 3500 miles on the rebuild with no problems.


SXP, I didn't notice much weight difference in the cylinder. Maybe they are using a thinner liner now? I'm not sure if the cylinder casting extends down into the crankcase or just the liner? It looks like the casting does and if so there was almost nothing left of it after it was bored for the liner. Did your liner have a taper in the bottom of it?
I can't imagine how anyone could get that ring in by hand. The few times I got it partially in I checked the oil expander with a magnifying glass and sure enough it had overlapped at the ends as per the warning that came with the kit. I could phsically get the ring into the cylinder by hand, but not without overlapping the oil expander(center wavy) ring. When I installed it with the ring compressor I slowly slid the barrel off of the piston until the bottom oil ring popped out and I could see the expander ring, and the ends were not overlapped.

  • SXP

Posted January 25, 2005 - 08:49 AM

#13

I guess I got lucky - who knows :cry: I did use the ends of two wooden rulers (as opposed to screwdrivers as Hamish suggested) to press the rings just so I wouldn't scratch anything, but I just don't recall fighting the thing.

The cylinder casting extends all the way down with the iron sleeve liner enclosed within it. I'll take a picture of the sleeved cylinder this evening if I can find it (did some cleaning up a while ago and can't remember where I put things).

  • Frostbite

Posted January 25, 2005 - 10:36 AM

#14

Maybe I'm losing my touch :cry: but the oil expander ring would always overlap when I compressed the 2 smaller keeper rings by hand. Did you check it for overlap?

  • TallBoysWRF

Posted January 26, 2005 - 09:36 AM

#15

Has anyone had problems with the extra heat due to the larger displacement? Is a higher volume coolant impeller necessary? :cry:

  • SXP

Posted January 26, 2005 - 11:35 AM

#16

Has anyone had problems with the extra heat due to the larger displacement? Is a higher volume coolant impeller necessary? :cry:


Nope!

I bet Frostbite's bike probably never ever comes up to ideal operating temperatures :cry: :cry:

  • Indy_WR450

Posted January 26, 2005 - 11:59 AM

#17

I hear Frostbite only uses 1 rad and the other is ready for back up. Bust a rad up there in the frozen Tundra and all you do is connect the other rad and pack it full of snow! :cry:

  • Frostbite

Posted January 26, 2005 - 01:56 PM

#18

I hear Frostbite only uses 1 rad and the other is ready for back up. Bust a rad up there in the frozen Tundra and all you do is connect the other rad and pack it full of snow! :cry:


Ha Ha, :cry: very funny boys and not far from true. I fell and crunched one rad(left side) and while I was waiting for the new one to arrive I just slipped a piece of 3/4 copper line into the hoses. I didn't notice any difference but I stuck the new one on anyway when it landed.
I get stuck on occasion in deep snow and to keep the bike from overheating while I'm trying to push it out I pop the rad deflector fins and pack the rads with snow. Even if it's starting to gurgle the snow on the rads will tame it down in a few seconds. So there's at least one benefit of riding up here. :cry: :cry: :cry:

  • doubledee

Posted January 26, 2005 - 03:36 PM

#19

Call Gary at Thumper Racing. :cry:
I have a Thumper racing WR280 Kit on my 2004 WR250 it's fast and reliable. :cry: I also have a 99 WR400 and would not hesitate to do a bigbore kit. If you want reliability to remain close to stock don't go too big. If you want absolute power go big but you'll trade off some longevity somewhere in the motor. :cry:

doubledee




 
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