Trailryder42

Member
Feb 6, 2000
295
0
Hey all,
I was advised to ask Eric Gore if he has an XR440 kit. Anyone know? I rode Cuzs' 440 this last weekend and it rocks. I guess Thumper Racing has a kit? Thanks for any info.
 

xrsforever

Member
Nov 2, 2000
249
0
My son has a 440 kit,and I have an 280 kit from Thumper.We both have been very happy. Largest single improvement you can do to an XR.Don't forget the SUSPENSION.:cool:
 

Trailryder42

Member
Feb 6, 2000
295
0
Powroll offers the kit in either 10.5:1 or 12:1 compression. Question: does it go: the higher compression ratio you run, the higher octane fuel required? or the other way around? What would be the assets and tradeoffs of one over the other? Thanks.
 

DualSportr

Member
Aug 22, 2000
527
0
The higher compression, the higher octane required.

With 12:1 you'll have to run straight, leaded race fuel - at least 110 octane.

Another option is the 415cc bore kit. This will create quicker reving power than the 440 kit, and some riders like it better. The 440 kit is best for torque and smooth power. The 415cc for rpm and quick power.

In a drag race on pavement, the 415cc kit will beat the 440cc kit. But in mud, the 440 kit will be better.

Hope this helps you out a little!
 

Rodzilla

LIFETIME SPONSOR
Jul 21, 1999
615
0
Hey Derek,

Check the XRs only website they have several different kits to punch out your XR. You may consider doing the valves and such while the jug is apart. I think I remeber Eric Gorr replying a Fellow DRN rider saying that going through him would be cheaper. But I may be talking out of turn on that.

I'm looking at the 430 kit as opposed to the 440. I hear you don't have to resleave with the 430 (again I'm not positive)

Looks like I'll be splitting cases this winter to replace my shift shaft so I might have Eric do a 430, port and valve deal on my 400 as well.

Let me know what happens

Rod
 

SFO

LIFETIME SPONSOR
Feb 16, 2001
2,001
1
The 400 is another motor that likes Stainless exhaust valves.
If you are popping it apart for a big bore, you might consider dropping good valves in it.
You will notice that your valve lash will require less attention.
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,820
16,889
Chicago
Originally posted by DualSportr

With 12:1 you'll have to run straight, leaded race fuel - at least 110 octane.

Keep in mind the MON (or motor) octane rating of the fuel is the significant spec in this case. There are a number of race fuels with high overall octane numbers (> 100) but a large gap between RON and MON octane ratings. High RON rated fuel without comparable MON rating is fairly useless in an air cooled XR.

PJ - Don't forget to remind these guys that the (MON) octane the engine will require is dependent on the CR and the cam they are running, specifically how late the intake valve closes. The later the intake valve closes the lower the MON octane required (all else being equal). Running a 12:1 CR with the stock XR cam run (at stock lobe center angle) will generate very high cylinder pressures and an enormous amount of heat and in my opinion it's not a good idea regardless of the fuel you are running. It's not a coincidence that Honda matched a relatively low stock compression ratio with the stock early intake close timing. :)

Trailryder - Unless your rides are short and the engine only sees light loads it's best to be conservative with the CR on these engines and make sure you match the compression ratio and cam timing carefully. Don't forget it's still an air-cooled engine :)
 

DualSportr

Member
Aug 22, 2000
527
0
I'm looking at the 430 kit as opposed to the 440. I hear you don't have to resleave with the 430

This kit leaves the stock liner VERY thin.

Not recommended for long piston life.

Rich, right as always - sometimes I just don't like to get that involved unless asked - I talk too much anyway (or should I say type too much!).

;)
 

Rodzilla

LIFETIME SPONSOR
Jul 21, 1999
615
0
Originally posted by DualSportr


This kit leaves the stock liner VERY thin.

Not recommended for long piston life.


;)


See this is why I spend time here. It reveals my ignorance.

So what you're saying is go ahead with the 440 as it will, in the long term, provide a better lifespan?
 

mtngoat

LIFETIME SPONSOR
Jun 12, 2000
314
0
I visited and chatted with the XRs Only crew last month and they were pretty hot on their 430 kit, which doesn't require the sleeve. They've always been pretty forthcoming with pros and cons of different approaches and didn't "con" the 430 solution because of thin walls. It'd be worth investigating that option and asking them IMHO. I know it's not the same since Al Baker passed away, but they still seem to have competent and honest staff.

I also recommend against very high compression. The XRs already run very high head temps and commonly "embrittle" valve seals causing them to smoke at start-up.
 

Wolf

doooode
Jul 31, 2000
2,487
1
I am extremely interrested in this thread.
Since I have not been very successful at selling my xr I may keep it and go to one of the above mentioned options. I wasn't sure I wanted to sell to begin with...
I am looking for a little more in order to have a chance at staying at least midpack at the starts, and have a little more snap out of corners in order to be able to clear some of these jumps that you don't have much time to set up for. Top end is of no significance to me since I am used to not having any to begin with. If any of this rambling made any sense, wouldn't that mean that by the above posted descriptions of the kits, the 415 would be better suited for me??
 

Rodzilla

LIFETIME SPONSOR
Jul 21, 1999
615
0
"The XRs already run very high head temps and commonly "embrittle" valve seals causing them to smoke at start-up. "

Yep, experiencing it now.

Rod
 

SFO

LIFETIME SPONSOR
Feb 16, 2001
2,001
1
I must confess, I can't figure out how a brittle valve seat would create smoking on start up.
I have seen high head temps on air cooled motors, turbocharged drag bikes and single cylinder rotaxes.
What I have seen is valve seats lose concentricity to the guide in high heat situations.
Also I have seen valve seats fall out. Putting new seats in a rotax head we would use .008-.010" interference, or press.
One or two mile races on a rotax and check your leak down.
The new liquid cooled stuff is nice because the heads keep a valve job longer.
 

mtngoat

LIFETIME SPONSOR
Jun 12, 2000
314
0
That's seals, not seats. If I remember right, the valve seals are akin to plastic. I'll find out this winter when I pull the heads off my XRs for valve jobs. Might be sooner on one though, it's smoking real bad at start-up.
 

SFO

LIFETIME SPONSOR
Feb 16, 2001
2,001
1
Like I'm a dummy.
Seals make a lot more sense.
Feel so stupid now.
You could check the guides as well, KMPI makes great ampco 45 guides that transfer heat better than the stock iron ones.
They are more difficult to size, requiring honing, instead of the oem reamers.
The results I believe are worth the effort.
They also make one piece stainless valves for this bike that will outlast the oe ones.
 

DualSportr

Member
Aug 22, 2000
527
0
Okay, let me apologize in advance - this will be a long one, but I wanted to answer a few different points brought up here.

So what you're saying is go ahead with the 440 as it will, in the long term, provide a better lifespan?

Yes, or do the 415cc kit.

They've always been pretty forthcoming with pros and cons of different approaches and didn't "con" the 430 solution because of thin walls.

I'm going to stick my neck out here - but here goes --
XR's Only has always relied on derivative technology - they don't design most of their products, but purchase them from other sources. Because they're not actually designing the product, they don't really know its limitations as well as the company that initially produced the kit.

They are very nice people. I like them very much. They are able mechanics, but I don't think I'd put them in the same class as a technician who designs and tests this stuff.

If you want to, ask them what the sleeve wall thickness is at the bottom of the sleeve after the 430cc kit is installed. If they can't answer this question quickly, then they have no way of knowing whether the sleeve thickness will be a problem or not.

The XRs already run very high head temps and commonly "embrittle" valve seals causing them to smoke at start-up

A stock engine will do the same thing - it's not really the heat that does them in - but the motion of the valve travelling up and down. Higher lift cams will cause this to happen much more quickly, and those will cause head temps to drop.

I do agree the high comp is not good for most applications. Especially trail riding.

If I remember right, the valve seals are akin to plastic. I'll find out this winter when I pull the heads off my XRs for valve jobs. Might be sooner on one though, it's smoking real bad at start-up.

Yes, the seals are made of a rubbery plastic material, with a metal retaining spring. If the engine only smokes at startup, it's definitely the seals. If you want your seals to last, use brown ones, or green ones.

If you purchased a gasket kit which includes stem seals, if they're black, throw them away and purchase the seals separately (they'll come brown or green that way). The black ones don't work at all.

BTW, for those of you who are used to doing valve jobs on automotive stuff, you might not know this;

On ALL Japanese motorcycle engines, the valves are stellite coated, and can't be ground! Even lapping them in more than a few strokes will cut thru the hard coating and you're back where you started. We've seen brand-new engines with cupped valves because they were over-lapped at the factory.

Cut the seats & grind the seats only.

Of course, the solution to this problem is Stainless Steel valves!

I am looking for a little more in order to have a chance at staying at least midpack at the starts, and have a little more snap out of corners in order to be able to clear some of these jumps that you don't have much time to set up for. Top end is of no significance to me since I am used to not having any to begin with.

It depends on your weight - if you're under 200 lbs, I'd go for the 415cc kit. If you have the extra cash laying around ($1,500), do a cam, hardfaced rockers, valve springs, an FCR carb and a 3 angle valve grind. This is really a pretty neat setup for motocross (but still not a YZF beater :( ).

The 440 produces more torque than the 415, but the 415 realizes the power much more quickly.
 
Last edited:

High Desert XR400

~SPONSOR~
May 21, 2000
151
0
PJ you never cease to amaze me!!! Powroll definitely gets my vote!
When I have "the extra cash laying around" I know where I'm taking my motor.;)
 

mtngoat

LIFETIME SPONSOR
Jun 12, 2000
314
0
Dualsportr, thanks for that info. I'll be sure to investigate seals when I redo my heads.

But, with the friendliest intentions, I have to stick my neck out too. While I agree, in part, with your "derivative vs. design argument", I think it understates the practical knowledge gained from application.

For instance, product reviews are underway here at the forum. One could argue that the reviewers don't know the limitations/capabilities of the reviewed products because they didn't design them. Practically, I think it's the application (i.e. end use) of a design that's most conclusive.

Back on point, I've found the XRs Only folks and others (e.g. Baja Designs) who use "derivative" technology to be the most informed about what works and don't. They also provide a valuable "feedback" loop to the designers, who aren't the ones most often fixing what didn't cut it in design.
 

Wolf

doooode
Jul 31, 2000
2,487
1
Mtngoat
Have you talked to the XR's only boys about the 430 kit and the points Dual sporter brought up? I am dangerously curious.

Dualsportr
As always, thanks for the info!!! I am 205 pounds so I guess I need more cc's;)
 

mtngoat

LIFETIME SPONSOR
Jun 12, 2000
314
0
Spoke with Steve at XRsOnly today. He said the 430 kit leaves the cylinder wall very thin. I didn't press him for a numerical value. But, he also said they've done a lot of them and no problems have been reported. They have done sleeves on a 430 kits too. The cost difference for a sleeve is ~$200. Considering all this, I think I'd opt for the sleeve or a smaller bore.

Here's a funny development. I asked them about valve seals. They confirm avoiding the black ones, but recommend red neoprene replacements. Red, brown or green; anything but black, I guess. I figure substance is more important than color.

One other area of interest is cams. Seems there are hard-welds (stock cores re-welded/ground), HRC/stock and a weird XRsOnly variant they claim is not hard-welded. Hard-welds require aftermarket "hard" rockers, HRC/stock and the XRsOnly variant do not. I have no clue how XRsOnly produces a re-ground cam with more lift/duration without welding material onto a core :think
Maybe something's getting inflated.

Anyway, longevity seems questionable with the hard-welds. There's conflicting opinions on this, but my dealer has built and re-built many 400 motors with hard-weld cams and claims they wear significantly faster than stock (which doesn't seem to wear much at all; ever heard of a cam failure on an XR?)

The HRC cam at ~$390 is twice the cost of aftermarket hard-welds. My buddy runs one and compared to my 440, it really runs strong top end, where my 440 excels on the low side. I'm wondering whether a pumper carb and cam might be a more effective cost/benefit combo for your track application.

BTW, I checked out the Powroll site and really liked it. I appreciate sites that educate in addition to profiling product.
 
Last edited:

DualSportr

Member
Aug 22, 2000
527
0
Back on point, I've found the XRs Only folks and others (e.g. Baja Designs) who use "derivative" technology to be the most informed about what works and don't. They also provide a valuable "feedback" loop to the designers, who aren't the ones most often fixing what didn't cut it in design.

What about companies who engineer, design, manufacture and test the product? What about companies who do all these things to many different products, then just choose the best to sell?

I agree there are many companies who spend years testing products much harder than some original manufacturers, and have better ideas about what works and what doesn't. But that doesn't preclude manufacturers from also doing testing which is just as good.

Regarding the Camshaft debate. After dealing with the RFVC engines since 1984, here is what the cam grinding companies, and other manufacturers have determined.

Due to the rocker/sub-rocker design that the RFVC head uses, an increase in lift from a "performance" camshaft results in a big increase of pressure on the camshaft & rockers.

Increasing camshaft LIFT will cause increased pressure on rocker and camshaft lobes.

Increasing camshaft DURATION will not cause increased pressure on rocker/camshaft.

The HRC camshaft increases duration without greatly increasing lift. This is how they are able to run a "performance" camshaft without using hardfaced rockers.

If the XR's Only camshaft is not hardfaced, then it is either Billet (made from a new core), or a re-grind.

A re-grind removes material from the base circle of the camshaft making the rockers drop down further towards the centerline of the camshaft. This allows a company to make an inexpensive grind that can increase lift and duration without actually having to add material onto the camshaft.

If XR's Only does not require a core exchange, then it's a Billet cam. If they do require a core exchange, it's a re-grind. Either way, since it does not require hardfaced rockers, it has an increase in duration, and not much of an increase in lift. I assume the cam will run with stock springs also?

Most aftermarket engine builders have found, after years of testing, that with the RFVC engine it is best to use hardfaced rockers with ANY change in lift or duration. It's cheap insurance against cam/rocker failure.

Also, there's a reason most aftermarket cams for the 400 increase the lift. Because the engine responds really well to it! Just an increase in duration does help, but not very much (gives more top end, but doesn't do much for midrange and throttle response stays about the same).

If you'd like more information about camshafts, check with the two cam grinders in the US who build aftermarket cams for the ATV and Motorcycle industry. Megacycle (415-472-3195) and Web Cam (909-369-5144)

These two companies grind about 99% of all aftermarket cams made for 4stroke singles. Both companies have been around a long time, and they both can explain the causes for cam and rocker failure better than I can.

These are the companies who supply Powroll, White Brothers, XR's Only, Thumper, and everyone else with their camshafts. Some companies (like White Brothers) just purchase the "house grind", other companies make up their own design and have megacycle or web do the grinding.

BTW, we have seen other kits sold by performance companies which made the stock liner "really thin" also (a 78mm piston kit for the XR250).
When you looked at the liner, you could actually see 'ghosting' where the piston left a mark on the bottom of the liner. The sleeve was essentially collapsing in on the piston during use.

The aftermarket company in question attributed the problem (seen in more than one instance) to improper installation, fuel wash, and/or ring failure.
 

John Blaze

Member
Feb 24, 2000
29
0
I've had the 440 kit in my XR for a year now and it sure makes a totally differnet bike out of it. Almost keeps up with my 500. :D But really I've done a straight drag with me on the 500 and a friend on the 442. Second gear about 3 bike lenghts and up in 4th it's got about 7-10. 500 sure feals faster though.
 
Top Bottom