Project XR600
George Couyant
*** Caution, some filth may follow ;-) The following article contains ***
*** certain references which may be interpreted as being filthy and ***
*** amazingly perverse. It may offend some readers, husbands, wifes, ***
*** uncles, aunties, pets and wall paper and may also encourage a ***
*** healthy interest in people of the oposite gender. There are ***
*** references to exhausts, heads, reaming, stroking, barrels, ***
*** pistons, relief, breathing, inlets, water, porting, abuse, ***
*** restricting, experimenting, choking, flowing, bending, power, ***
*** creaming, grunting, sliding, watering eyes and heaven forbid, ***
*** Mikuni carburetors.....Then again, maybe you won't be offended ***
*** so it's probably worth while reading on. ***
*** This warning and the following article aren't meant to offend ***
*** nor is it meant to alienate any readers (it's all toungue in ***
*** cheek, ok? ;-^ ;-^ ;-^ Hope you had a chuckle. I did. ***
*************************************************************************
A good riding buddy recently bought a new XR600 and over the last month or
so we've been doing a bit of work on it to make it a competitive race
mount. We concentrated mainly on making go faster without sacrificing
reliability and we think we've found a cure for the gearbox gremlins.
If you're interested, read on.....
Firstly, the stock gearing made its way to the dust bin and was replaced
with a 50 tooth rear sprocket.
Front and rear suspension went straight to XR's Only for progressive
springs and a revalve (the rotton sod wouldn't let me modify them..maybe
just as well...). The idea here was to keep its lovely slow speed damping
and complience but firm up the mid stroke onwards so that it'll handle
big hits properly. The result was amazing. It feels much firmer and more
stable at speed. You can hit obsticles at speed and it takes it in its
stride.
Off came the barrel and it was sent away for a 630cc kit. They wanted to
stick a 12:1 high compression piston into it but we went for a "more sane"
11:1 piston (the 11:1 will run better on 97 octane pump gas). When we got
it back, we assembled the head onto the barrel to check valve - piston
clearance with the cam we planned to run (mild one which has a big lift
boost over stock, but timing and overlap are close to stock). We were
surprised that there was so little clearance and it meant we had to do
something. The choices were to either recess the valves deeper into the
valve seats or fly cut valve reliefs into the piston. I left it up to the
owner and he tossed a coin...we fly cut the piston.
The cam was a little tight in its bearings and whilst it would free up
somewhat after a bit of running, I decided it would be best to give it a
bit of room. The owner is a fitter and turner and his shop has a neat NC
machining centre, so we spent a day farting around aligning everything up
and gently reamed the cam bearings. The cam now spins true and free. A
real improvement and well worth it.
Next we needed to improve the breathing. Another mate has a Muzzy motor in
his XR and we got a chance to measure the porting on that. What they've
done is remove a lot of material in the inlet tracts to straighten the
flow path and made them a hell of a lot wider. If this had been a water
cooled head, I'd never have attempted this sort of porting for fear of
hitting water jackets....But port we did. The alloy is really soft (softer
than my TT600's) and I had trouble keeping the porting tools from clogging
and marking the finish (maybe it's time I overhauled my porting tool to
get a bit more speed out of it..). If you're attempting it, be careful.
The finished product looks good though and you can clearly see the inlet
valves through the ports. The exhaust ports were ok and just got a bit of
a cleanup. This was a really good casting with stuff all slag. Along with
top quality silicon valve springs, the top end should be bullet proof and
be able to hang together at high rpm.
The gearbox is a problem on hard working XR600's. The hard facing on
3rd and 4th gears (sometimes 2nd as well) wears and they break with
potentially disasterous results. Since it's damn near impossible to get
better quality cogs, the only thing left is to lessen the stress on them.
We had heard that a clutch from an NX650 can be used to increase the
primary drive gearing. This will lessen the load on the gearbox since it
will spin the gearbox drive shaft faster. You can make adjustments to the
gearing later by increasing the size of the rear sprocket to compensate.
He took the plunge and spent a heap of money on a new NX650 clutch
assembly and primary drive. Hope it's worth it....only time and much
throttle abuse will tell....
With everything bolted together, the bike ran well but it was clear that
the carby and exhaust was too restrictive. The thing would go like a
rocket and then run flat up top.
We first exeperimented with the carby by removing that shit choke
butterfly. This thing really restricts air flow and I still wonder why
they persist with it. The TT600's choke system is great in comparison.
This made a big difference to the top end. If you want instant noticeable
power increase, simply remove the choke butterfly! Only problem is that
it's a bear to start when cold. This would clearly piss me off, so I
borrowed a square slide 41mm Mikuni (the stock carb is a 39mm Keihin) and
grafted that on. Talk about a difference! This thing hauled! I think he'll
buy the carby.
For the exhaust, we wanted to bolt on the exhaust off an early model XR
(pre '91) because they breathed better, but couldn't get one for a
"reasonable" price. My mate ended up making a great looking set of headers
out of larger diameter tubing. There are smoother bends and it flows much
better than stock.
So what's it like?? I was really impressed with the final product. It's
like a really strong XR with power everywhere. On it's first ride, the
mate with the Muzzy motor came along and whilst the Muzzy motor would pull
away at the very top end, this XR would cream it in the low and mid range.
Much easier to ride and dare I say easier than a stock motor. Because it's
got heaps of grunt and is very controllable, you can leave it in 3rd or
4th all day...and oh those power slides! I had about an hour of riding on
it on the day and it was hard giving it back. Lifting the front end for
logs and obsticles was a breeze. Just twist the throttle from zero rpm in
2nd or 3rd. No messy wheelspin, just gobs of tourque. Hit the open stuff and
your eyes water! Big 5th gear power slides without once stepping out of
line (mind you, I didn't want to drop his new pride and joy so I never
went *really* crazy)..
It was interesting for me jumping straight back on the TT600. It felt big
and whilst I have the TT set up stiffer, this XR seemed more stable when
cranked right over in a bend. The TT felt fat and heavier. The XR steered
better in the tight stuff too, though when flat out at speed, the TT was a
class above. Power wise, down low they were about the same (TT's motor mods
are similar) with the TT having an edge in the mid range. Up high though,
the XR would hang on for what seemed like another 500 rpm.
One thing we did notice though was that a lot of oil was being blown down
the crank breather pipe. We're told it's common when revving hard and
there's a simple mod to the oil pump to fix it. I'm a bit concerned by it
because none of the other XR600's I know of have this problem.
If you have some cash sitting around, spend it on these mods. You'll never
believe the difference. I want one.
George C.
Mike McClendon
This must have cost a fortune; what were the most cost-effective mods that
would be well worth our hard-earned $'s?
-- Mike
George Couyant
> Subject: Re: Project XR600
>
> Did you do anything to the ignition, like Roost Boost?
Nup. I'm not convinced that a Roost Boost gives value for money.
All we did on the ignition side of things was to advance the
ignition timing 2 deg and run a one grade colder plug. There's no
sign of pinging, so we can probably advance it a bit more...but
it'll do for now.
>
> This must have cost a fortune; what were the most cost-effective mods that
> would be well worth our hard-earned $'s?
All of 'em!!! ;-)
Well, it didn't cost heaps (except for the clutch). Most of the
The suspension was a few hundred and the 630cc kit was a few
hundred as well. The rest was late nights. We even welded
additional cooling fins on the head (rather than paying XR's Only
to do it). The carby will cost a few hundred as well but it's
worth it. Since the motor was new, we could reuse gaskets (seen
the price of an XR's gasket kit lately?....gag...matter of fact,
seen the price of any gasket kit lately?...gag...gag...How about
$40 for a TT600's head gasket...gag..gag...gag...).
The cheapest mod is to remove the choke butterfly...It made a heap
of difference..pity it makes it hard to start in the morning.
Best value for money mod was suspension. Progressive springs,
revalve, good quality fluid. I reckon XR forks can be made to work
as well as any of the exotic mega buck forks. The good thing with
XR forks is that they will still flex when they take a big hit. It
cushions your hands and arms. Stiff USD forks don't. The rear end
got a better quality spring and revalve to stiffen compression
damping near full travel. 10wt fluid up front and 5wt in the
shock.
The 630cc kit? Hell, why not. If I was stuck for cash, I wouldn't
bother. I'd rather spend it on the cam and valve springs/retainers
and porting. There are enough cc's there to begin with. It's just
that XR's stock breathing is a bit asthmatic. The exhaust was
remarkably easy to make. If you've got a welding outfit (not an
arc welder....) and a big vice, you can make it no sweat. If you
have access to a pipe bending machine, it's even easier. We
didn't, so we crafted a few pipe mandrels to keep the pipe round
as we bent it. For the severe bends, we filled the pipe chock full
of sand (from the kids sand pit) and plugged the ends before
bending (keeps it from flattening). It's a matter of constantly
trying it on the bike, comparing it with the stock pipe and
bending. A bit like fitting Bark Busters....Shaping and welding
the join where the two headers meet into one was tricky.
This could have cost him thousands of dollars if he had a shop do
it all for him with off the shelf parts. I'd say that he did it
all for under $1,500 AUS plus a few weeks of late nights. When you
compare the total cost to say a Husky 610TE, he's laughing.
I'm kind of interested in doing something similar for me now. The
TT's getting on a bit and I can't afford a 610.
Cheers
George C.
Mike McClendon
be made to rotate, then lock in place at whatever timing position is best --
and would the performance gain justify the effort?
> The cheapest mod is to remove the choke butterfly...It made a heap
I would think the next cheapest for big returns would be changing to the
high-compression piston, yes?
> arc welder....) and a big vice, you can make it no sweat. If you
I don't know if I have a big vice, but my wife points out plenty of little
ones . .
-- Mike
Neal Howard
warnings preamble to your article:
"fly", "being blown", and "hard"
Neal Howard
ne...@cmptrc.lonestar.org
'91 XLH-1200
'70 Kawasaki 100cc (old fossil, but it still works, sorta)
==============================================================================
George Couyant
>
> How? Drill out and remount the pulse generator? Do you think the PG could
> be made to rotate, then lock in place at whatever timing position is best --
> and would the performance gain justify the effort?
The holes at the base of the coil are already slotted, so all you
have to do is chip away the resin they use to lock the screws etc
and loosen them. Move the coil and lock it back with new screws
(just a safety precaution, but it's worth it for a few cents) and
check the timing again. If it's ok, get some resin (electrical
supply store) and paste it up much like you found it. Don't go too
thick though because it's weaker.
Most XR's and TT's can take a bit more advance over stock without
pinging. They are usually tuned to run on 92 octane unleaded. Our
leaded pump gas here is 97 octane (readily available at any
station), so it's worth advancing the timing. It is free horse
power after all...If you notice any pinging though, back the
timing off. If you can see small silver deposits on the inner
porcelain post in the spark plug, back the timing off again
because you've got aluminium from the piston melting and depositing
itself on the plug. There's no quicker way of junking a motor.
On XR's you'll also find advancing will help eliminate that
momentary hesitation when you crack the throttle off idle...You know
the problem I mean....weaving your way up a tricky hill..the motor's
hot...back off a bit...gas it to clear that step.....cough...stall.
..oh shit...lose your balance and tumble back down the hill...
everyone else laughs at ya and uses your fallen bike to help jump
that step.....but you get back at them at the next black, smelly bog
hole that little bush critters seem to love to die in.......
BRRRAAAAPPPP splash..HA HA HA HA ....got ya!
>
> > The cheapest mod is to remove the choke butterfly...It made a heap
>
> I would think the next cheapest for big returns would be changing to the
> high-compression piston, yes?
Nup, I think that cam and head work will give you the noticeable
boost. A high comp. piston will make it run more efficiently, but
won't give you much more hp. You're not letting it breathe any
better...and XR's respond well to breathing mods.
.....but while you have the head off, why not put a better piston
in....
>
> > arc welder....) and a big vice, you can make it no sweat. If you
>
> I don't know if I have a big vice, but my wife points out plenty of little
> ones . .
....and after a few years, all those little vices become big
vices..
Cheers
George C.
George Couyant
> Subject: Re: Project XR600
>
> Hey George, you forgot to put the the following words/phrases in the
> warnings preamble to your article:
> "fly", "being blown", and "hard"
Yea, I figured I had 'em covered when I noted Mikuni carburetors..
hee hee eh?
George C.
Jeff Deeney
> ************************************************************************
> *** Caution, some filth may follow ;-) The following article contains ***
> *** certain references which may be interpreted as being filthy and ***
> *** amazingly perverse. It may offend some readers, husbands, wifes, ***
It's a damn good thing that I read this whilst the wife and kids were in
bed. The cat, being a cat, couldn't care less. :-)
> A good riding buddy recently bought a new XR600 and over the last month or
> so we've been doing a bit of work on it to make it a competitive race
> mount. We concentrated mainly on making go faster without sacrificing
> reliability and we think we've found a cure for the gearbox gremlins.
Sounds pretty impressive. Tell me though, what kind of racing is he using
this bike for? It seems that this would have to be open desert to even
come close to making use of that power. Scott Summers runs a stock engine
on his XR, but most of his riding is in the woods. Scott also uses up 5-6
XR600s each year. It would take a team of mechanics to build trick XRs for
that guy.
> boost over stock, but timing and overlap are close to stock). We were
> surprised that there was so little clearance and it meant we had to do
> something. The choices were to either recess the valves deeper into the
> valve seats or fly cut valve reliefs into the piston.
Another alternative would have been to insert an extra base gasket. The
only drawback is a little loss in compression.
> If you have some cash sitting around, spend it on these mods. You'll never
> believe the difference. I want one.
If I had the time and cash, I just might. If I just had the cash, I'd
probably buy a new Husaberg. :-) Did he do anything to lighten up the
bike? I've heard the the XRs are unwieldy fat pigs in tight woods.
-Jeff Deeney- KotD #0000 DoD#0498 NCTR '88 XR600-Shamu
j...@hpfcla.fc.hp.com AMA#540813 COHVCO '81 CB750F-Llamaha
We don't stop riding because we get old, we get old because we stop riding.
David Donald
Jeff and George, talking about a MAJOR FAST XR600, finally leads to:
>If I had the time and cash, I just might. If I just had the cash, I'd
>probably buy a new Husaberg. :-) Did he do anything to lighten up the
>bike? I've heard the the XRs are unwieldy fat pigs in tight woods.
Now Jeff, how can you say that... Scott Summers seems to have no problems
at all... course, he's bigger than Hulk Hogan...:)
>We don't stop riding because we get old, we get old because we stop riding.
We also get sore because we stop riding... at least, that's what I found out
when I went riding for the first time in 4 YEARS this weekend... it's good to be back!!
Dave
--
| don...@dvinci.usask.ca | "Its 106 miles to Chicago, we've got|
| Communications Systems Research Group | a full tank of gas, half a pack of |
| University of Saskatchewan | cigarettes, it's dark, and we're |
| Saskatoon, Canada | wearing sunglasses." "Hit it." |
Mike McClendon
cylinder and conceal it in the petrol tank . . . and watch those CR500 guys
turn green with envy as you blast by 'em on the hills!
-- Mike
Al Conte
>cylinder and conceal it in the petrol tank . . . and watch those CR500 guys
>turn green with envy as you blast by 'em on the hills!
Yeah ! I'll be sure to bring my camera and take a picure of you and your
rip snortin, fire breath'in boat anchor going ballistic into the trees !!!!
Al
Tim Zantow
Great Article!
I have plans for my XR.......
Ciao, Tim
Tim Zantow AMA# 152574
ti...@sdd.hp.com
619-592-8107 (work)
619-488-8919 (beach)
91' Honda XR600 | Let's go riding!
85' Husky WRX400 | Mexico!
Bob Maccione
>
>Scott Summers runs a stock engine
>on his XR, but most of his riding is in the woods. Scott also uses up 5-6
>XR600s each year. It would take a team of mechanics to build trick XRs for
>that guy.
>
really, seems that none of the articles mention that, what I've read is that
he seems to run the same bike all season with minor mods. It would be
interesting what he breaks on the bikes.
bob
anasaz!bo...@asuvax.eas.asu.edu
George Couyant Convex Support
From: j...@hpfcso.FC.HP.COM (Jeff Deeney)
> Subject: Re: Project XR600
>
> Sounds pretty impressive. Tell me though, what kind of racing is he using
> this bike for? It seems that this would have to be open desert to even
> come close to making use of that power. Scott Summers runs a stock engine
This guy ain't no Scott Summers, but he is a speed freak...he is
human after all...
The bike's an enduro mount for our Victorian Enduro Series held
mainly in our high country. It's probably the wrong bike for this,
but who cares. It'll be a lot of work fun. It'll also be
his fun trail bike for our play rides...
I'd hazard a guess that Scott's stock motor is mainly for
reliability.
> Did he do anything to lighten up the bike? I've heard the the XRs are unwieldy fat pigs
Nup. There ain't much you can do is there....
Cheers
George C.
George Couyant
> Subject: Re: Project XR600
>
> Yeah ! I'll be sure to bring my camera and take a picure of you and your
> rip snortin, fire breath'in boat anchor going ballistic into the trees !!!!
Yea....just point it and shoot. CR500RR's a bit like that..
Hee hee
George C.