How to increase the power of a '94 XR600?

[mikyrc]

First of all, hi to all That's my first post here.

I'm from Spain so my english isn't perfect. I don't know if there's anybodyelse from Spain here.

Well I own a '94 XR 600 with supposedly only 6k miles or so.

But i feel that lacks a lot of power.

I had a new XR600 on the '92 and i can remember that this bike were a lot more powerful.

So i guess it's time to do a head rebuild or rebore and put a new piston. It still doesn't eat a lot of oil but there's something not right there.

When cold there's oil smoke during few seconds. And the rear guard is a bit brownish due to the exhaus gases.

I have an aftermarket muffler, but stock headers. All wrapped with heat wrap.

I was planning to upgrade it a bit as i usually use it on the roads.

I was thinking of putting a NX650 dominator cylinder with an oversized xr piston to gain some power. But i've read that the 2nd or 3rd gears tend to break if the power is increased too much.

Is that thruth?

What else can i do to gain some horses all across the rpms and isn't too expensive?

Thanks.

Here's my bike:

[DaveySprocket]

Hello and welcome!

There are many different things you can do to get more power out of the motor, some being more expensive than others. I am sure it is possible to make the Dominator cylinder/piston work, though I am not sure what would be involved since I believe the Dominator has a longer stroke.

I just finished rebuilding my 94 600R with some performance parts and the power increase is huge! I went with a 98mm (610cc) 10.5:1 piston, HotCams cam, head work, carb, exhaust, etc. You can see the full write-up here:

www.daveysprocket.com/projects/xr_610.html

If you want to spread out costs over time, I would rebuild the engine with a larger piston and cam, since you can easily add external parts (carb, header, etc) afterwards.

Dave

[mikyrc]

Thanks Dave. Good job on your modding man!

That XR looks very powerful.

I think i'll look for different upgrading methods and then decide what to do.

For the bigger piston you just bored the stock cylinder to the new size, right?

Is it taller too? As you were looking for valve clearance or it was because of the new cam?

What kind of gas do you use? We use 98Ron that is like your 91 MON gas.

DO you know where can i get aftermarket parts like the piston, cam, etc. online? Ebay maybe?

And about your head port job. What exactly did to the ports? Just smooth the walls or did you enlarge them too?

Thanks a lot Dave.

[Jon-D]

what bike is that rear wheel off of? I ride mine on the street and would like to convert if possible.

[wr450fyamaha]

what the hell is goin on with that rear wheel?

[mikyrc]

Hi guys.

That wheel is from a Suzuki GS500. It fits almost perfect. You just have to torn (shave, wear,.. i don't know the right word) a bit the brake side and make the brake disk cut to the right size as it's bigger in diameter.

[mikyrc]

I think i'll convert it to 628cc, because if i put a high compression piston i'll have to use high octane gas and here we have 91 as much.

Daveysprocket, please can you help me with what i asked you a bit above?

Thanks to all.

[DaveySprocket]

Thanks Dave. Good job on your modding man!

That XR looks very powerful.

I think i'll look for different upgrading methods and then decide what to do.

For the bigger piston you just bored the stock cylinder to the new size, right?

Is it taller too? As you were looking for valve clearance or it was because of the new cam?

What kind of gas do you use? We use 98Ron that is like your 91 MON gas.

DO you know where can i get aftermarket parts like the piston, cam, etc. online? Ebay maybe?

And about your head port job. What exactly did to the ports? Just smooth the walls or did you enlarge them too?

Thanks a lot Dave.

Hey there,

Yes, the cylinder was bored to accomodate the new piston. I checked for valve clearance since I was changing cams and because I do not trust companies to make parts correctly. The first piston I got from xrsonly was completely wrong, so I would not assume the second one was correct. Checking clearance is easy insurance rather than damaging your motor when you try to first kick it over.

I use 91 octane cas, which is generally the best you find here in California. You should be fine as long as you do not get too high on the compresion ratio (I am using 10.5:1).

As far as parts, I am not sure. As I mentioned, I went with XR's Only, but will never use them again. Complete nightmare from start to finish. Perhaps BarnumsPro? I do not see engine parts on the site, but maybe email them and see what they have?

As far as the porting, I just smoothed out any rough or uneven spots, like the seams along the port walls, etc. You want to leave a bit of a rough texture though, as that helps heep the fuel suspended in the air. The old idea of "polishing" turned out to be a bad idea. I also made a nice sharp edge where the intake flow is split into two ports. This is just to keep turbulance down and get a good flow through that path.

Does that help?

Thanks and good luck!

Dave

[mikyrc]

Hey thanks Dave it helped a lot.

I searched at barnumspro and they only have stators for the XR600, but no problem i'll look for parts on other sites.

Thanks again.

[bork]

Hey thanks Dave it helped a lot.

I searched at barnumspro and they only have stators for the XR600, but no problem i'll look for parts on other sites.

Thanks again.

You better contact them(barnum), They were into baja & more. They do it all. Rob is really great to work with. Good knowledge.

[CrusaderSpaw]

A couple more questions about the wheel.

Do you know what year that Wheel was? Did you have to replace the XR's Rear brake? And was it the front or back...(I assume the front seeing that it would be the smaller of the two.) Do you think it would work for a 97 XR600R? I'm trying to convert mine to a supermoto. Thanks... By the way nice setup.

[floydstar]

Hi DaveySprocket

Would love to read all about your build as am just starting mine.  This link doesn't work anymore - is this still available somewhere?

I just finished rebuilding my 94 600R with some performance parts and the power increase is huge! I went with a 98mm (610cc) 10.5:1 piston, HotCams cam, head work, carb, exhaust, etc. You can see the full write-up here:

www.daveysprocket.com/projects/xr_610.html

Many thanks, Dan.