Can someone confirm fitment of bigbore components


23 replies to this topic
  • AUSmoker

Posted February 20, 2015 - 10:14 PM

#1

I will be rebuilding my WR400 next week.

Despite some mixed views and opinions, i have been given some financial aid to get the job done. Im not debating if i should, but how.

Apart from inspecting and replacing parts needed, im looking to upgrade. I dont need the power, but like it, so no debating there either.

Can i simply get a 426 cylinder, bore it to 444, replace piston, pin, and rod?

What else can i do, or another option to increase power.

I would be a bit upset if rebuilding it gave me no more power, and only got rid of the knock.

It has an aftermarket muffler and decomp exhaust cam. Unsure of kms or anything else. It will be used mainly as a road bike.

No need for debating if i should do it, im basically getting it rebuilt for free but performance upgrades are a cost to me only.

All advise is encouraged, including shops for parts in Australia.

Thanks

  • grayracer513

Posted February 21, 2015 - 06:49 AM

#2

If you are still using the original exhaust cam without auto decompression, a simple trick is to retard the exhaust cam one tooth.  This changes the cam timing to match that of the YZ400, which will give you a significant power boost. 

 

Either that, or a set of aftermarket cams like the stage one Hot Cams for the YZ400 (or just the exhaust cam) equipped with auto decomp to get the power gain along with a much simpler starting routine.



  • AUSmoker

Posted February 21, 2015 - 08:53 PM

#3

It does have the decomp exhaust cam.

Does an intake cam make much difference?

  • grayracer513

Posted February 21, 2015 - 09:56 PM

#4

Not very much. The OEM intake cams are the same in both bikes, and Hot Cams stage 1 are only a little more aggressive than stock YZ.



  • fmxr47

Posted February 24, 2015 - 08:20 PM

#5

I just last year got my scattered wr400 engine back together because of finances it took forever, I'm a Yamaha certified tech just so people know I'm not a dumbass haha, but I threw a 426 jug on there with a 03-05 450 piston(same wrist pin DIA. As 400 con rod) and same bore as a stock 426 I believe 95mm I'm going from memory, been about a year, the piston I chose was a wiseco 13.5:1 I do believe and the deck height and interference to the valves all checked out, I've only got a few hours on the bike since the build but I'm pleasantly surprised with the results, I also retarded the exh. Cam 1 tooth.

Edited by fmxr47, February 24, 2015 - 08:21 PM.


  • AUSmoker

Posted February 28, 2015 - 05:09 AM

#6

I just last year got my scattered wr400 engine back together because of finances it took forever, I'm a Yamaha certified tech just so people know I'm not a dumbass haha, but I threw a 426 jug on there with a 03-05 450 piston(same wrist pin DIA. As 400 con rod) and same bore as a stock 426 I believe 95mm I'm going from memory, been about a year, the piston I chose was a wiseco 13.5:1 I do believe and the deck height and interference to the valves all checked out, I've only got a few hours on the bike since the build but I'm pleasantly surprised with the results, I also retarded the exh. Cam 1 tooth.


So the 450 piston fit a normal 426 jug? Is it just the stroke os dofferent to make the 450?

Isnt the 400 rod considered weak when putting a bigger piston on??

  • AUSmoker

Posted February 28, 2015 - 05:10 AM

#7

Also is that a hogh compression piston needing special fuel?

  • fmxr47

Posted February 28, 2015 - 05:29 AM

#8

Yes the bore of the 426 & 450 are identical, the stroke is the difference. To be honest idk that the 400 rod is weak or not, I don't remember anyone having any reliability issues. And when it comes to fuel the stock 400 or 426 recommended octane is 92+ I believe, so I just run 93.

  • AUSmoker

Posted March 04, 2015 - 11:50 AM

#9

Well my plan is a 426 rod for a bit better durability (since its apart) a wiseco 444 pison to suit the bored and nikasiled 426 cylinder, new plug, oil, filters,cam chain, main bearings, gaskets seals and possibly;

1.High comp piston (we have 98 RON in AU equivalent to US AkI 93 so not sure if thats safe..

2. New valves, springs and retainers since there so old I like reassurance. No idea of cost however.

3. Possible port and polish the head, but need it sent a long way away, also VARY expensive from what I have seen. If i get new valves do they clean up the head at all anyway?

4. Considering a powerbomb header. Its got a stock one now but with aftermarket muffler. I also heard grinding out a bit of a sloppy weld in the header helps And that stocks not too bad???

5. Debating whether to get an intake cam while im at it.

Really not sure whether to skip the cam, valves and porting for now, or maybe do a bit or??...

Ideally it all at once would make it pretty tough bit of kit.

What would you do?

Oh i read there was a weak woodruff key sprocket that can get replaced with a geared sprocket to stop it coming loose, any ideas on that.

Its going to cost a packet but at the end of the day i can have a heap of power for the sandy enduro tracks, and get a set of SM wheels for a blast around the street

  • grayracer513

Posted March 04, 2015 - 01:13 PM

#10

Well my plan is a 426 rod for a bit better durability (since its apart) a wiseco 444 pison to suit the bored and nikasiled 426 cylinder, new plug, oil, filters,cam chain, main bearings, gaskets seals and possibly;

1.High comp piston (we have 98 RON in AU equivalent to US AkI 93 so not sure if thats safe..

2. New valves, springs and retainers since there so old I like reassurance. No idea of cost however.

3. Possible port and polish the head, but need it sent a long way away, also VARY expensive from what I have seen. If i get new valves do they clean up the head at all anyway?

4. Considering a powerbomb header. Its got a stock one now but with aftermarket muffler. I also heard grinding out a bit of a sloppy weld in the header helps And that stocks not too bad???

5. Debating whether to get an intake cam while im at it.

Really not sure whether to skip the cam, valves and porting for now, or maybe do a bit or??...

Ideally it all at once would make it pretty tough bit of kit.

What would you do?

Oh i read there was a weak woodruff key sprocket that can get replaced with a geared sprocket to stop it coming loose, any ideas on that.

Its going to cost a packet but at the end of the day i can have a heap of power for the sandy enduro tracks, and get a set of SM wheels for a blast around the street

 

  1. 98 RON is more than adequate
  2. Do the valves.  It's a lot cheaper with the 400, as the bike uses stainless valves at about a third the cost of titanium or less
  3. Don't bother with any of the port work.  Too expensive for too little gain on such an old bike that wouldn't really be a competitive race bike anyway.  And please avoid any temptation to do it yourself.  The 3 valve intake presents a unique set of challenges to porting, such that it's much more likely that you'd loose power rather than gain it if you don't know how to work the port.
  4. The benefit to the power bomb is a wider power curve, not more power.  I wouldn't spend for one unless it was used.
  5. Cams?  Get the "stage one" exhaust with automatic decompression.  I'd run the stock intake if it were me.

Regarding the key, it's a square key, not a Woodruff, and it indexes the balancer shaft drive gear to the crank.  The key is not weak, per se, but the crank gear nut has a tendency to work loose, which lets the gear rattle, which beats up the key, and eventually the crank.  This was replaced in 2001 by a splined gear, but converting to it requires the use of an '01 or '02 crankshaft to go with it.



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  • AUSmoker

Posted March 10, 2015 - 07:59 AM

#11

Well I ordered the bigbore kit.

426 cylinder to 444 and nikasiled, new piston (i went with standard compression as not all fuel stations have 98, plus i believe it will give me a bit more life out the engine).

Ordered kibblewhite valves and seals, keeping original springs for now.

Not getting an intake cam, and it has the exhaust cam already.

Keeping the standard exhaust and other components, just new main bearings and gasket/seal kit.

I will be getting the head cleaned up for the valves, but no porting work.

Other than a new cam chain and the above, hopefully it will be fixed and reliable with some more power In the next week or two.

FYI i saw the engine apart today and the rod moved up and down atleast 5mm. The mechanic said it was the worst he had seen without the engine blowing. The piston had taken off the nikasil in one small area and messed up the piston skirt.

How long before the first oil change and or valve check, and any particular run in procedure?

  • grayracer513

Posted March 10, 2015 - 08:16 AM

#12

Break-in.  Start the engine, check for oil pressure and circulation, leaks, etc., get the idle baselined, then shut it off and check everything while it cools just a little.  Start it and ride it around at no more than 50% of its capability for ten minutes, then shut it down and recheck things.  Then fire it up and ride it for 20 minutes at up to 85% of it's capability for another 10-15 minutes.  Assuming no problems have turned up, take it out for another ride for 20 minutes or so and run it fairly hard, up to 95% of its capability.  At that point, break-in is over, and you can run it any way you like. 

 

Do not either baby the bike, nor beat on it hard for the first 45 minutes to an hour.  Lugging the engine and revving it out to the limit are one as bad as the other during this time.  It needs the pressure to be put on it to quickly and thoroughly seat the new rings, but it also needs time to run all the moving parts in well, too, so the key is to strike a balance. 

 

Change the oil after the first hour.  Use a top quality motor oil for break-in, not some cheap stuff.  break-in is a critical time, and good lubrication is extremely important.



  • AUSmoker

Posted March 10, 2015 - 11:29 PM

#13

Break-in.  Start the engine, check for oil pressure and circulation, leaks, etc., get the idle baselined, then shut it off and check everything while it cools just a little.  Start it and ride it around at no more than 50% of its capability for ten minutes, then shut it down and recheck things.  Then fire it up and ride it for 20 minutes at up to 85% of it's capability for another 10-15 minutes.  Assuming no problems have turned up, take it out for another ride for 20 minutes or so and run it fairly hard, up to 95% of its capability.  At that point, break-in is over, and you can run it any way you like. 
 
Do not either baby the bike, nor beat on it hard for the first 45 minutes to an hour.  Lugging the engine and revving it out to the limit are one as bad as the other during this time.  It needs the pressure to be put on it to quickly and thoroughly seat the new rings, but it also needs time to run all the moving parts in well, too, so the key is to strike a balance. 
 
Change the oil after the first hour.  Use a top quality motor oil for break-in, not some cheap stuff.  break-in is a critical time, and good lubrication is extremely important.


Greyracer,thanks.

I have just been told the crank that has cam chain teeth is worn and needs replacing.

Also the oil pump, it has scratches and grooves from where the inner and outer 'wheels' rub on the case.

I have been quoted by the mechanic $1000au for a new crank and nearly $400 for an oil pump.

Can I just get the two wheels for the oil pump instead of the whole assembly? And get the case grooves polished out a bit?

And I cant find aftermarket cranks!

Please help, i just spend over $1600, plus its going to be about $1100 for install and odd parts, now this!!!

  • grayracer513

Posted March 11, 2015 - 06:48 AM

#14

Post a picture of the crank sprocket.  Almost all of them show significant wear, but lots of them go back into service anyway.  If you want to replace the whole crank, look for a Hot Rods crank for a 426.  You may have to buy  a crank gear if the new crank comes with a splined drive end for the balancer gear.



  • AUSmoker

Posted March 11, 2015 - 07:55 AM

#15

I will need to post pics tomorrow.

I have found some better pricing for an oem 426 crank, the extra gear needed and an oem new oil pump for just under $500us to my bill.

  • AUSmoker

Posted March 12, 2015 - 02:53 AM

#16

See pics.

What do you think??

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  • grayracer513

Posted March 12, 2015 - 07:03 AM

#17

The crank sprocket is worn, but serviceable as is.

 

Replace both oil pumps, and replace the drive pin for the scavenging pump (the one in the case).

 

In your pictures of the scavenging pump cavity, you don't have one that shows the rotor pocket without the outer rotor in the way, but it looks in usable condition. 



  • AUSmoker

Posted March 12, 2015 - 07:26 AM

#18

The crank sprocket is worn, but serviceable as is.
 
Replace both oil pumps, and replace the drive pin for the scavenging pump (the one in the case).
 
In your pictures of the scavenging pump cavity, you don't have one that shows the rotor pocket without the outer rotor in the way, but it looks in usable condition.


Can you please explain what drive pin you are referring to? A part number maybee? Or is it the one in the picture.....

Actually I think i understand what you wrote, i was going to buy the complete assembly in my hand, and the rotor still in the case.

When the rotor in the case was removed, there is the same scoring in concentric circles in the case. Does that need to be sanded out or what.

Thanks

  • AUSmoker

Posted March 12, 2015 - 07:36 AM

#19

http://www.partsfish...78e402/oil-pump

  • grayracer513

Posted March 12, 2015 - 08:07 AM

#20

You need items 1, 2, and 3.







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