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Discussion Starter · #1 ·
Just tore down a 450xc motor out of a Outlaw. The squish is alot bigger then what I am used to seeing. The head gasket measured .045" and the piston sits in the hole .027", thats a total of .072". I didn't measure the base gasket, I would prefer to keep a gasket there. Would .035 to.040" be to much to ask out of the stock crank and rod? What gaskets is everyone running?

Another thing I noticed is that the combustion chamber is huge for a 450cc machine, I guess this is a plus if you are planning on going the big bore route, but with a 89mm piston there is no squish pad?

I have not flowed the head yet, the ports csa looks alittle big considering the rpm range of bore/stroke I will post the numbers and a graph here when the time comes. I know that I am definately going to need a better quality valve and valve job right off of the bat. It looks like ktm has put a bandaid vj for soft oem intake valves. There is not much room on the valve adjuster if i decided to sink the valve to correct the vj it's gonna be pretty close to running out of lash adjustment. Probally gonna have to bump up to 36's

I am not sure of the compression, cam or pipe I am planning on using yet. Race gas is not a problem, just not sure of the stregth of the stock rod? Does ktm use Mahle pistons? Aperance wise it looks like the Mahles I use in some of my sbc dirt track motors. Open to opinions.

Intake system is definately going to take some modding, not much of an air filter assy

I am a builder by trade, just never messed with the ktm's much. Nothing against them just not many around here, but that seems to be changing. This one will be built for a b class motocross rider. I probally would have went a different route but my brother/sister in law was thinking that this was the same engine as the ktm sx quads because Polaris called this the Outlaw mxr

Any tips or sugestions would be greatly appreciated
Sorry for all the questions guys,
 

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jump over to the KTMTALK web page and get into the RFS forum, lots of good details there.

KTM Talk

These engine respond well to head work and it's a known issue withthe soft intake valves.

Rod: due to the long stroke thing gets a bit marginal if you rev em hard all the time, apparently Baldwin has a special Falicon rod for these engines.

Again plenty of information on KTM talk.
 

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Discussion Starter · #3 ·
Thanks for the link, gonna check it out. Yeh, the bore /stroke combination seems like it would be better suited in an xc quad. I guess KTM relized this when they built theirs. The sx looks like it's gonna be a revver. Oh well, I guess I will have to try and make this one competitive even though it seems like the underdog against the competitions over-square bore/stroke type of machines used for mx..... The mid-range hp & tq might be alittle easier to ride for an intermediate rider.

I don't know if what I have to share is worth anything or not, but if I knew it all I would not be here asking question in the first place.......

First thing first, I will try and post some flow #'s for the stock head along with some velocity readings. Then I will calculate the needed csa of the port to make pk hp at the desired rpm compared to the csa in the head and run the spec's through a few software programs. Thats a good question, Whats a safe rpm to shoot for with this motor? Whats the stock limiter set at?

The few runs that I have seen, make peak hp around the 8000-8250 range.

It's always fun for me when I get a motor that I have no experience with. Lots of wheels get to turning and sometimes they do turn backwards. It's all part of the learning curve, sometimes it gets to be frustrating, but in the end, the results of accomplishment is well worth it.

The chassis/suspension is someones elses territory, my main goal is based on the powerplant......Anything thats obvious, needing attention or what to stay away from feel free to jump in
 

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Thanks for the link, gonna check it out. Yeh, the bore /stroke combination seems like it would be better suited in an xc quad. I guess KTM relized this when they built theirs. The sx looks like it's gonna be a revver. Oh well, I guess I will have to try and make this one competitive even though it seems like the underdog against the competitions over-square bore/stroke type of machines used for mx..... The mid-range hp & tq might be alittle easier to ride for an intermediate rider.

I don't know if what I have to share is worth anything or not, but if I knew it all I would not be here asking question in the first place.......

First thing first, I will try and post some flow #'s for the stock head along with some velocity readings. Then I will calculate the needed csa of the port to make pk hp at the desired rpm compared to the csa in the head and run the spec's through a few software programs. Thats a good question, Whats a safe rpm to shoot for with this motor? Whats the stock limiter set at?

The few runs that I have seen, make peak hp around the 8000-8250 range.

It's always fun for me when I get a motor that I have no experience with. Lots of wheels get to turning and sometimes they do turn backwards. It's all part of the learning curve, sometimes it gets to be frustrating, but in the end, the results of accomplishment is well worth it.

The chassis/suspension is someones elses territory, my main goal is based on the powerplant......Anything thats obvious, needing attention or what to stay away from feel free to jump in
I'm guessing you are limited to 450cc's. The RFS platform did have a over-square bore/stroke 450. this combo was found in 450 sx's and 450 SMRs. It used a 63.4mm stroke crank and a 95mm bore. It used a shorter cylinder and shorter cam chain but everything else is the same. It would use the head you already have and the engine cases are the same. It might be worth looking into.
 

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Discussion Starter · #5 ·
I'm guessing you are limited to 450cc's. The RFS platform did have a over-square bore/stroke 450. this combo was found in 450 sx's and 450 SMRs. It used a 63.4mm stroke crank and a 95mm bore. It used a shorter cylinder and shorter cam chain but everything else is the same. It would use the head you already have and the engine cases are the same. It might be worth looking into.
Yeh, would like to keep it at 450cc. The shorter stroke and bigger bore sounds interesting. Any particular year to look for? I am KTM ill-literate
 

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Yeh, would like to keep it at 450cc. The shorter stroke and bigger bore sounds interesting. Any particular year to look for? I am KTM ill-literate
2003-2006 450SX has that setup. If you can go to 453cc you can use a easier to find 400 crank a 525 cylinder and a thumper racing 453 piston to get a similar setup, only difference is the 400 crank has .6mm more stroke.

The 450sx piston is 59030007000 I, crankshaft 59030018600, cylinder 59430005000, cam chain 59036013000

hope that helps
 

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Discussion Starter · #7 ·
Does the 400 use a longer rod then the 450sx crank? Just assuming the 525 cylinder is the same height as my current set-up. Is the difference in the compression height of the pistons? Probally be alittle easier to get a pipe to bolt up using this setup.

Sounds like it's easier then I thought to change this motor between a "lugger" and a "revver". In fact the bore and stroke combinations available are better then any other single I have been involved with.

Know the question of valve float is stirring around in my mind. To take advantage of the over-square bore/stroke combinations mentioned above your definately going to have to turn the engine at higher rpm limit. After a certain ve% percent with the same stroke/bore setup, the only way you are going to make more hp is with an increase in rpm's where peak hp is achieved. Where does the 450sx's seem to make peak power at? Do they run a lightened version of the same rocker arm I am dealing with? Ti valves? With the mass weight of the rocker set-up, it's going to take a pretty good set of springs.

I guess the biggest problem would be the stock rev limit of the Outlaw?

How about timing chain problems?

Just trying to weigh my options here, for every positive thing it seem like there is always negative side. Some good info. coming, thanks guys
 

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Does the 400 use a longer rod then the 450sx crank? Just assuming the 525 cylinder is the same height as my current set-up. Is the difference in the compression height of the pistons? Probally be alittle easier to get a pipe to bolt up using this setup.

Sounds like it's easier then I thought to change this motor between a "lugger" and a "revver". In fact the bore and stroke combinations available are better then any other single I have been involved with.

Know the question of valve float is stirring around in my mind. To take advantage of the over-square bore/stroke combinations mentioned above your definately going to have to turn the engine at higher rpm limit. After a certain ve% percent with the same stroke/bore setup, the only way you are going to make more hp is with an increase in rpm's where peak hp is achieved. Where does the 450sx's seem to make peak power at? Do they run a lightened version of the same rocker arm I am dealing with? Ti valves? With the mass weight of the rocker set-up, it's going to take a pretty good set of springs.

I guess the biggest problem would be the stock rev limit of the Outlaw?

How about timing chain problems?

Just trying to weigh my options here, for every positive thing it seem like there is always negative side. Some good info. coming, thanks guys
Yes the 400 has a longer rod and a taller piston. the 453 will not rev like a 450sx because the piston is heavier. The SX engines used a lighter flywheel and had Ti valves in the head but the heads and valve train are the same other than that. The Outlaw would more than likely use the same CDI box at the KTMs and IIRC the stock rev limit for them are 9500 and the SX's had a 10500 limit but the SX's peak power was made lower than 9500. They said on KTM talk that the higher limit on the SX's was for more overrev potential. Timing chains seem to last a good while, at least 2 valve jobs.
 

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the SX internals are a big job

the XC engines makes a real nice mxer for alot of riders, lots of good useable tractible power. These engines really get of the line hard. I really enjoyed racing the XC in club MX.

I'd develop the head / cam / valve train first, you'll be surprised how much better it will go.

KTM 806 cam works well (basically that the SX cam) / FMF megebomb header and rear can of your choice (FMF or DASA).

Maybe look at 41mm bore on carb.

IF he then wants more rev power then look at the SX crank deal. Not sure though if the XC flywheel setup is compatible ???

Best thing would be to develop the chassis - SX axle / SX a arms / better shocks once basic engine work has been done. The XC handles alot better when it's sitting lower / wider
 

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Discussion Starter · #10 ·
the SX internals are a big job

the XC engines makes a real nice mxer for alot of riders, lots of good useable tractible power. These engines really get of the line hard. I really enjoyed racing the XC in club MX.

I'd develop the head / cam / valve train first, you'll be surprised how much better it will go.

KTM 806 cam works well (basically that the SX cam) / FMF megebomb header and rear can of your choice (FMF or DASA).

Maybe look at 41mm bore on carb.

IF he then wants more rev power then look at the SX crank deal. Not sure though if the XC flywheel setup is compatible ???

Best thing would be to develop the chassis - SX axle / SX a arms / better shocks once basic engine work has been done. The XC handles alot better when it's sitting lower / wider
The chassis/suspension is someones elses territory, my main goal is based on the powerplant.

I do agree, that it does not matter how much hp/tq you have, if you can't get it to the ground or use it, what good is it? I believe that having the correct suspension under a mx type of machine is just as important as a good powerplant for a fast rider. For someone just starting out, I would opt to run the stock engine with upgraded suspension components.

I am not sure of the suspension company they are working with, but I do know that they are working on a wider, Lt arms/shocks for the front and a Lt set-up for the rear.

I did find out why thy went with Polaris, according to my brother-n-law, the shop that they bought the bikes at (2 of them) is going to sponsor them. Not sure of the details, just told me that he got a good deal on the quads and that they were going to help him out on parts, race fees, etc......Not many Polaris's out on the track around here competing at this level, I guess they want to change the way that everbody looks at them. Most folks seem to buy them for trail riding, racers all get a smerk on their faces when they see them out on the track. It's a marketing thing that I would prefer to stay out of.

The more I think about the motor, I'am gonna give the stock bore/stroke combination a try first. Then if things don't work out, I will try a different combo. One of my biggest concerns is, my nephew is going to have to adapt his riding style to suite the power delivery of this engine versus the "screamers" that he has been riding.

Can't seem to post any pic's or screenshots on here.....Figured I would post some runs of a stock bike versus last years race bikes (hondas). Nothing real wild, made 33 ft. lbs. tq. and 55 or so hp at the rear wheels on a dynjet 250ix dyno. Thought it would be intersting to the other viewers to see the way the power comes on vs's a "ex" style motor.

Can't seem to find spec's on different cams available, doesn't seem to be alot available
 

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KTM make 4 differnt cams, plus Hotcams have a profile

general consensus is that the 806 KTM SX cam is the best for the 450 engines.

see my post way back on cam profiles

cams.
 

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Discussion Starter · #12 ·
kiwi-craig, Thanks for thr info. on the cams. As it ussually goes for me, the answer to one question tends to lead to more questions.

I see that all the measurements are @ .040". I guess that you would have to add that to the max lift?

Are these measurements directly off of the cam? Just wondering if I would need to take into consideration the rocker arm ratio?

Sure would be nice to have some intake CL's and LSA. The characteristic's of a cam can be greatly influenced by these numbers. A quick search on the hotcam gave me it's LCA's of 113 deg. on the intake and 111 deg on the exhaust. Any one with more info. on this would be greatly appreciated.
 

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Discussion Starter · #13 ·
It was brought to my attention by another member on another forum, that if you're going to be running at 9000RPM a lot of the time, it would probably recommend polishing the crank and switching to ball bearings instead of the factory roller bearings.

Just wanted to pass on the info.
 

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ball bearing low end conversion is common especially with the stroker engines.

stock rod is nothing flash either but probably fine in a 450.

the details on the cams came from CUT 7 over on KTM talk. Apparently the 8/33 and 8/07 are best suited to big bore engines and the hot cam profile tends to give up low end due to less than stellar LCA configuration. I run the 8/06, it's really nice, picks up where the stock cam goes breathless and give a nice linear pull on the top end.

cut 7's notes: These are raw figures taken with the cam on spindle & a dial indicator directly on the lobe; so they don't reflect the true valve lift & duration. However, they are very close, & can be compensated for the rocker ratio with some simple mathematics. Because the RFS motor is a roller rocker, the duration at the valve won't change much. More importantly, the relationship between each cam is true & correct.

Because we didn't measure them in the motor, I don't have opening & closing figures (before & after TDC) nor do I have lobe separation angles. Travis & I are going to try to degree all the cams in a motor next week, which will give actual valve lift. However, I do know that the rocker ratio is 1.147:1. So to get actual valve lift for say, the HotCams intake cam, multiply 1.147 times the raw lift (9.42mm) which equals 10.8mm. This jibes with what HotCams has on their website.
 

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kiwi-craig, Thanks for thr info. on the cams. As it ussually goes for me, the answer to one question tends to lead to more questions.

I see that all the measurements are @ .040". I guess that you would have to add that to the max lift?

Are these measurements directly off of the cam? Just wondering if I would need to take into consideration the rocker arm ratio?

Sure would be nice to have some intake CL's and LSA. The characteristic's of a cam can be greatly influenced by these numbers. A quick search on the hotcam gave me it's LCA's of 113 deg. on the intake and 111 deg on the exhaust. Any one with more info. on this would be greatly appreciated.


.040 is a reference point. Its .040 valve lift and then the measure duration from .040 off opening to .040 before closing and this is how you calculate your duration.

Most automotive cam company's use a industry standard of .050
 

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Discussion Starter · #16 ·
Thanks for clarify how they came up with the numbers. I could picture the duration numbers at the .040" mark, but on top of the spec. sheet "Camshafts lift & duraration @ 1mm (.040").

I guess I was putting more into then I should of. I do understand how to calculate duration no.'s at 1mm or the .050" mark. I was thinking that they started measuring max lift from this point. It didn't make much sense to me, thanks for clarifying things.

Moto Headz, would you happed to have any more detail on camshafts available for the rfs engine. Spec.'s on lca's or lsa's angle would be greatly appreciated.
 

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so we are talking a straight axle outlaw ? get a rath racing airbox kit, the stock unit is pathetic and you are seriously risking the engine with the stock filter in place. The stock polaris exhaust belongs on a motormower...... bin it......
 

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Discussion Starter · #18 ·
so we are talking a straight axle outlaw ? get a rath racing airbox kit, the stock unit is pathetic and you are seriously risking the engine with the stock filter in place. The stock polaris exhaust belongs on a motormower...... bin it......

Yeh, it's got a straight axle. They are already have the rath airbox kit coming. I have not seen it yet, but anything has to better then the oem unit on there, what a joke.

Probally end up making my own head pipe and mid-pipe and adapt it to another can. Most of the head pipes available are not the right tuned length/diameter. I guess it would be near impossible for a mass produced pipe to be the best pipe for every build out there. There are alot of factors that dictate the proper tuned length. There has been alot of books written on this very subject. I don't fully understand the whole process and have yet to talk to anybody that can say, they do 100% understand the exhaust side of the engine. It seems like there is alot of conflicting ideas/information out there. I have come up with some useful formulas from here and there and of course a lot of trial and error.....On my TRX builds I found another 3 hp/2tq at peak without a loss anywhere in the rpm range (much flatter tq curve) over the best production pipe that I have tested (dasa). Just by making my own head pipe and adapting it to the dasa. Most don't fully understand how a properly tuned exhaust will effect the Intake side of the engine. Combine a good tuned intake and a tuned exhaust reults in alot of power being unleashed. If I can get this thing to make power, get alittle free time on my hands, maybe do simplified write up on the subject
 

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I know for a fact this exact quad is capable of doing some amazing things. I've watched Doug Eichner put himself in his own zip code in races at Glenn Hellens and 395 Raceway. So don't beat yourself up to much on this motor combination in the MX class. It will hold it's own with the best of them. It may not be the best combination out there but that is what makes the mechanic a true mechanic. Your tenacious thinking and inovation will make the others look in astonishment when you go by them on a regular basis. I like the idea of lightening and balancing the rotating assembly plus welding the crank pin and installing the ball bearings on both sides of the crank. This should increase the reliability to almost bullet proof. Good luck with your build. I'm watching from the side lines with great anticipation of your success with this rfs engine in the quad.

Brian
 

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Discussion Starter · #20 ·
Pops, thanks for the words of encouragement.

I have in one hand the, stock bore/stroke combo on a serious diet, and in the other hand the same motor with sx internals. Both have there good and bad points, the worst part of the sx swap is it's not the most cost effective to build or reproduce. I would like for the other members/owners of this type of engine to be able to reproduce the build.....Just my way of saying thanks to all that's helping.

Of course, this will be easier said then done for someone without the proper equipment. Most builds get pieced together piece by piece instead of a complete bottom/top-end build. There is a lot of reputable shops that can lighten and balance/weld the rotating assembly when the funds become available and they are wanting to take the build to that next step. This step would not be one for everybody, but for the few looking for that extra edge and durability. Most of the weight saving come as a durability issue and is hard to notice by looking at dyno runs in hp/tq. This set-up really shines on a loaded dyno doing back to back acceleration runs
 
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