Big Bore Kit for WR400?



16 replies to this topic
  • Richard56

Posted February 04, 2004 - 04:32 AM

#1

Since on the market there's big bore kit for XR400 to convert into a 440... Is there any big bore kit for a 98' WR400 to maybe a 450? By the way, if I change the cyclinder, header, piston and the thing that pushes the piston up and down... will it fit into a 98' WR400 engine frame and becomes a 450?
Just asking to be sure... But these sounds a bit wierd right? :)

  • SXP

Posted February 04, 2004 - 05:13 AM

#2

The largest RELIABLE hop-up kit I've heard of is the 430 kit made by Thumper Racing (see my ongoing woes with them in this thread - http://www.thumperta...5/o/all/fpart/1

  • MN_Kevin

Posted February 04, 2004 - 05:44 AM

#3

also:

http://www.eric-gorr...fourstroke.html

  • SFO

Posted February 04, 2004 - 06:38 AM

#4

I would whole heartedly endorse upgrading the crank/rod assembly to the later style 19mm wrist pin of the 426.
I have seen a few grenaded 400's that had big bore kits in them. It tends to wipe out the motor when the rod pokes out of the cases. New crank assembly from YOT is under 320$.
Go all the way and get a 426 cylinder punched out to 97mm and get a 444cc!.

  • SXP

Posted February 04, 2004 - 07:52 AM

#5

Is the crank-rod assembly from a 426 a straight drop-in replacement for the 400's? No other modification (piston excluded) needed? TIA.

I would whole heartedly endorse upgrading the crank/rod assembly to the later style 19mm wrist pin of the 426.
I have seen a few grenaded 400's that had big bore kits in them. It tends to wipe out the motor when the rod pokes out of the cases. New crank assembly from YOT is under 320$.
Go all the way and get a 426 cylinder punched out to 97mm and get a 444cc!.



  • MN_Kevin

Posted February 04, 2004 - 08:19 AM

#6

crank/rod, piston, pin need to be swapped.

  • PowerFiend

Posted February 04, 2004 - 12:44 PM

#7

I would whole heartedly endorse upgrading the crank/rod assembly to the later style 19mm wrist pin of the 426.
I have seen a few grenaded 400's that had big bore kits in them. It tends to wipe out the motor when the rod pokes out of the cases. New crank assembly from YOT is under 320$.
Go all the way and get a 426 cylinder punched out to 97mm and get a 444cc!.


Or get the parts and ship everything off to Powroll for a 2mm stroker to make a 469cc. :)

  • MrBlahh

Posted February 05, 2004 - 02:04 AM

#8

No reliability problems from mine, 426 jug bored out 2mm with custom wiesco piston, putting at at 444cc.

I have a spare crank, I need to get a 426 rod pressed on so I can use a proper piston.

Anybody stroked a WR400/426 yet with a 450 crank?

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  • Frostbite

Posted February 06, 2004 - 11:59 AM

#9

Did you bore the stock cylinder and have it replated or press in a sleeve? I have a cross country race coming up on March 27 and was thinking of popping in Thunder Racing's 430 kit. Then I found that Millenium Technologies can bore and replate the stock barrel, no iron sleeve. Anybody have any comments on this? I've been reading some of the posts here and am a bit worried about getting my scooter back together in time for the race.

  • PowerFiend

Posted February 06, 2004 - 12:54 PM

#10

Did you bore the stock cylinder and have it replated or press in a sleeve? I have a cross country race coming up on March 27 and was thinking of popping in Thunder Racing's 430 kit. Then I found that Millenium Technologies can bore and replate the stock barrel, no iron sleeve. Anybody have any comments on this? I've been reading some of the posts here and am a bit worried about getting my scooter back together in time for the race.


Bore and replate is the best option. Steel sleeves wear out a lot faster than a plated one and there are no small incremental piston upsizes to buy. Steel sleeves are old technology.

  • Eddie Sisneros

Posted February 06, 2004 - 05:07 PM

#11

Then I found that Millenium Technologies can bore and replate the stock barrel, no iron sleeve. Anybody have any comments on this? I've been reading some of the posts here and am a bit worried about getting my scooter back together in time for the race.



they are great!they will use a aluminum sleeve and replate it if a sleeve is needed.stay far away from the iron liners!

  • Frostbite

Posted February 06, 2004 - 05:57 PM

#12

Thanks boys.

  • hondahater1

Posted March 02, 2004 - 04:09 PM

#13

milenium tech can bore and replate your cylinder, I had it done to mine and it works great, regular turn around time is im thinking 3weeks, but being early in the year it may not be that bad, you also may be able to pay more to get it done faster. if its a 400engine, you can get the 95mm piston to make it a 426 plus you can increase the compression to 13.5. You can get the 97mm piston for it, but you will have to put the 426 conecting rod in it because of the larger wrist pin diameter. if you have a 426engine go to the 97mm piston and raise the compression to 13.5, it kicks A. milinium tech can do this for you, also US crome can do it to. best bet is to call them and see about the turn around time.

  • trailsnail85

Posted March 02, 2004 - 05:08 PM

#14

so if you have the 426 already then all you have to do is have the cylinder bored and resealed and then get the larger piston and pop it on.

  • SFO

Posted March 02, 2004 - 05:50 PM

#15

milenium tech can bore and replate your cylinder, I had it done to mine and it works great, regular turn around time is im thinking 3weeks, but being early in the year it may not be that bad, you also may be able to pay more to get it done faster. if its a 400engine, you can get the 95mm piston to make it a 426 plus you can increase the compression to 13.5. You can get the 97mm piston for it, but you will have to put the 426 conecting rod in it because of the larger wrist pin diameter. if you have a 426engine go to the 97mm piston and raise the compression to 13.5, it kicks A. milinium tech can do this for you, also US crome can do it to. best bet is to call them and see about the turn around time.



You will need a 426 barrel to make a 97mm bore.
You can only go to 95mm on the 400 barrel.

  • hondahater1

Posted March 03, 2004 - 04:23 PM

#16

yes, you send your cylinder, and the new piston to US chrome or milinium tech and they will bore and replate your cylinder to fit the piston, or tell them which piston you want and they will get it for you.

  • hondahater1

Posted March 03, 2004 - 04:28 PM

#17

not true! I had my WR400 cylinder bored to fit the 97mm piston (that is 200thousands of an inch), there is still plenty of material, and it has been that way for 3years with no problems




 
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