XR 600 Rebuild, Wiseco or Honda???


10 replies to this topic
  • mrholshot

Posted January 05, 2005 - 09:50 AM

#1

I am getting ready to rebuild my 1986 XR 600 because it has serious blowby and is hard starting. I am either going to go with a Honda .25mm over piston or a Wiseco 9:1 or a Nix Pro-X. I also plan on putting a stage 1 hot cam in it and cleaning up the ports and combustion chamber in the head. Also, should I go with expensive Honda valve springs or the spring kit offered by Parts unlimited? Trying to get it all rebuilt as cheap as possible and still be reliable. Don't want to put any more than $400 into it. Also, what is the best gearing for this setup, I weigh 185lbs and it is geared 14/45 now. Mostly open trails and some sand dunes. Thanks, Jason.

P.S. Any tips or tricks or anything I need to check while I have it down would be greatly appreciated

  • HeadTrauma

Posted January 05, 2005 - 01:36 PM

#2

This is just hearsay on my part, but I have read about the Honda pistons being slightly more accurate and consistent as far as matching the bore size they are marked as. However, if you give the piston to whoever is boring the cylinder, they can easily machine them to have the proper clearances(which should probably be done anyway). If the piston prices are the same, I would get forged. Often the aftermarket slugs have deeper and/or bigger valve reliefs which give you more options for a cam and headwork. Honda valvesprings are stock Honda valvesprings. I dont know who makes them for Parts Unlimited, but they are probably similar. Look at other places like Hotcams(they have springs too, right?), XRs Only, etc. Unless the ports have casting flash and crud, I wouldnt do much to them. Honda typically makes ports that hard to improve on and are easy to mess up. Polishing the chamber isnt a bad idea, though. For gearing I run 14/48, which I think is stock. It is much better than the 13/48 I had previous. I do all-around riding ranging from open roads to tight single track and I'm happy with my setup. Since you do alot of higher speed riding, you might just keep what you have until it all needs replacing.

  • XR6's_rule

Posted January 06, 2005 - 04:10 AM

#3

Whitebros valve springs would be a worthwhile investment, as they are stiffer and of better quality than the Honda items. Other than this, stick with genuine.

If you are chasing more power I did some mods to an XR6 last year with encouraging results.

1. Stick with the Honda piston as they are lighter than the aftermarket ones. To get more compression you can deck the cylinder head about 0.5mm. This achieves a compression ratio of around 9.8:1-10:1. To counteract the slight cam chain adjustment loss of this you can add material (weld) to the tensioner to gain more adjustment.
2. Also with the head whilist reseating the valves I smoothened the inlet ports without altering them to any degree. The aim is to give a smoother/faster fuel/air flow into to the combustion chamber. This will improve power in higher rpm.
3. If you can afford it, install a good aftermarket full exhaust system that would improve breathing.
4. Jetting will not need to be altered to any large degree. With my XR6 I only had to go one size larger on the main jet. You may need to go one range cooler with the sparkplug for eg I used a DPR9-EA9 instead of DPR8-EA9.
5. Heavy-duty clutch springs (I used White-Bros) will be required to counter the extra power output of the engine. If your clutch was slipping or showing signs of wear before the rebuild, replace the plates as well.

Summary- With these simple and inexpensive mods, the power boost is very good. For a comparision, I used a piped/jetted '99 WR400 as a yardstick at the time, and excelleration was neck and neck after the 600 would pull about 1 bike length ahead at the begining of a drag race. The bike covered about 3,000 dirt kms (2,000 miles) after I completed these mods, no breakdown or failure had occured whatsoever, I attribute this to the fact that all stock engine parts were used (except for clutch springs as mentioned above).

  • mrholshot

Posted January 06, 2005 - 06:34 AM

#4

Thanks for the replies! XR6's rule, what year 600 was this and could you run it on 89 pump gas? Was this with or without the full exhaust?

  • XR6's_rule

Posted January 07, 2005 - 02:18 AM

#5

It was an '88 XR600RJ, but you would get the same results with a later or earlier model. I ran 95 octane premium unleaded most of the time but it ran fine on 91 octane, no pinging. Using 95 octane will give you a touch more power. The bike I modded ended up with an aftermarket muffler (staintune) but had the standard stainless header pipes. I would recommend larger bore headers as these would give you even more power in higher revs!

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  • XRMANU

Posted January 12, 2005 - 02:22 PM

#6

. To counteract the slight cam chain adjustment loss of this you can add material (weld) to the tensioner to gain more adjustment.


How much do you add ? 2 a 3mm?

  • XR6's_rule

Posted January 13, 2005 - 02:18 AM

#7

For memory I added a good bead about an inch long around the part where the actual tensioner contacts with the guide then carefully grinded it back to the original rounded shape.

  • XRMANU

Posted January 13, 2005 - 02:31 AM

#8

How thick?

  • XR6's_rule

Posted January 13, 2005 - 03:04 AM

#9

About 3mm thick but it doesnt need to be exact, 2-3mm will do fine you're only compensating for a slight loss of adjustment.

  • XRMANU

Posted January 13, 2005 - 03:08 AM

#10

thx :cry:

  • bootlegger2

Posted January 14, 2005 - 03:31 AM

#11

i just got my cylinder done with the wiseco but they only come .5 mm oversizes for the 4-strokes which didnt make much difference to me stock compression is what i was lookin for i touched up the intake side and really slicked up the exhaust i done a valve job too nothing was removed from my head though the tension add on is a good idea though if you take some off the head
i dont think you realy gain any power from a higher octane gas it just keeps you from spark knockin your piston to death for the higher compression unless you can adjust your timing you dont realy gain anything from it it could actually slow you down





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