KTM ATV HQ Forums banner

8/07 cam install - gotta grind the head for clearance

10K views 20 replies 7 participants last post by  GotRoost? 
#1 ·
decided to try the 8/07 and found some interesting stuff, had to clearance the head on the exhaust side for the lobes to clear the casting, just touching the head casting on the intake lobe actually ! and the exhaust lobe was way to close for comfort......

Couple of minutes with the porting tool fixed that easy enough, pics to follow

clearance from the valve spring edge to the rocker arms is real tight also, any of you you guys notice this with 8/07 installs ? using the dual KW spring set. Doesn't touch but not allot of clearance, anyone actually putting a bit of a clearance radius on the rocker arms ? Rather not touch them but will get in there with some feeler gauges to check.....

seems strange since I'm coming off a Thumper stage 5 which is supposed to be more aggressive, maybe a different - smaller base circle
I never really noticed but maybe it was running real close.....

seems my exhaust rocker swivel feet are not great either having a hell of jobs getting the clearances set right........ cupped after 35hrs of heavy use ?? could be I guess......

going to try the 1/6 turn adjustment method

http://ktmtalk.com//index.php?showtopic=468282&hl=valve+clearance
 
See less See more
#2 ·
Never had clearance issues with my 8/07s. Ran them in 2 different engines. I didn't really look at it that close on install, since they were supposed to be drop-in. But the heads never had any damage when I tore them down.

As I've said before, as woods-riders go, I'm a high-RPM rider and the only clearance issues I had was with the valves kissing the piston during float if the springs were fatigued. I just made sure the OEM springs never got beyond about 50 hours old and it took care of it.
 
#4 ·
Camera lens Gas Reflex camera Audio equipment Office equipment
Gas Household hardware Machine Machine tool Auto part
Automotive tire Rim Automotive wheel system Gas Electric blue
Automotive tire Rim Gas Auto part Machine
Automotive tire Motor vehicle Rim Automotive wheel system Gas


I can see how the slight variation in the head casting would allow some to clear, others not........ mine actually left a wipe mark on the head when I turned it all over checking everything...... probably could have run actually but "zero" clearance..... NOT...... swipe with the die grinder and all sorted.....
 
#5 ·
tricky bit was masking the head off with tape and cotton wipes so i could grind it in place..... liberal use of grease as a grinder chip catcher, allot of wiping clean then used aerosol cleaner with the engine upside down to be sure it was spotless...... then a bucket load of compressed air as well.......

I can see why the engines guys use engine stands, would make life so damn easy.......
 
#6 ·
I have experienced the same thing with one head I had my stage 6 cam in. After closer inspection it appeared there was a little core shift in the casting that may have been part of the issue. Also with the stage 6 you will get some interferance between the rocker and spring retainer. I blend them a little with a sanding wheel to achieve .040 or so clearance.
 
#7 ·
yup, lloks like the case with the 807 - rockers to springs as well, more fiddly measuring..........
 
#8 ·
its odd that the 807 has this problem. Maybe your valve installed height is getting a little off. Have you measured it?
 
#9 ·
get 20 thou on the intakes, rocker to edge of retainer, but exhaust is less than 10thou, have 5 thou on the valves and the rocker is free to move but..........

GRRRR all coming apart AGAIN........

dunno. new exhaust valves, they did just touch the seats apparently to make sure they are true..... maybe it was the boy on the job...... fuck me........

intakes untouched.

frigged if I know, tempted to put the stage 5 back in............ or try the 8/33..... gads......

the SX-F looks more and more like a true gem compared to this pig........
 
#10 ·
thats to close for comfort. I would open the gaps a little to give you a little safety buffer.
 
#11 ·
30 thou plus on the intakes and 20 thou plus on the exhaust rockers, small sand paper wheel in the die grinder, all nicely blended...... job done........
 
#12 ·
nice work! and its really not to bad to do. This is an area I check on all the ktms i build now
 
#14 ·
if your serious about MX, save yourself allot of aggrevation and buy the SX........... miles better race engine overall
 
#15 ·
Interesting that you say that, though I not going to doubt ya on it either. I just said that as I currently have 08 525xc that I used to pro race and have never had any issues with it. And it spanked the hell out of high powered anything that I raced with. Including my 53horse built for racing raptor 700. And I am not easy on it in any way. I had seen so much ify things about sx's that I was a little skeptical though you do seem to be the man when it comes to how well these things hold either xc or sx . So I will be watching and reading even closer before I do actually by one or the other.
 
#16 ·
This kind of stuff is all part of growing pains with power output. We just seem to be hearing about it a lot more because the pushing is being done by members here who report issues to the community. All the four stroke engine platforms face similar issues. They have just been taken care of in the past by the shops that were doing the pushing on them. Both the xc and sx engine platforms have there place and can be made strong and reliable race engine if the proper steps are taken.
 
#17 ·
the big difference is the SX's ability to rev hard and freely, makes a huge difference on the track, you have to shift the XC engine more and actually have to work harder keeping it right in the meat of the power, yes it has way more torque but the lack of top end rev means your nudging the limiter all day long and shift shift shift..... plus the gearing is to short all mx tires I have to run 15/36 to be anywhere near right, and for the forestry stuff I run 16/36.

What i have learn't is trying to make the long stroke engine into a rev head highlights all the weaknesses of that engine, crank flex, timing chain stretch, ponderous valve train, general mechanical harshness..... each of these issues where addressed by KTM when they designed the SX-F platform for the two wheelers, super rigid crank, ultra short timing chain, better valve action, lots of safe over rev capability.

I far prefer to MX race the SX over the XC that for sure. Both are good in the dunes, but I'd give the nod to the XC's big torque numbers. Dune use running at 80% of max is where the XC shines, beefy easy power, trying to get 100% out of it and hard revving it just doesn't like it and sure doesn't last compared to the SXF.

34 hours and the XC has been down to the cases 3 times and the top end out 5 times............. 68 hp / 44 ft lbs, 9500 rpm limiter

110 hrs on the SX, just onto it's third piston and a bit of preventative maintenance inside, I did have a crank main bearing issue - went noisey at 30 hrs didn't fail but wan't happy. 63 hp / 36 ft lbs 11,700 rpm limiter. Zero mechanical "failures" never let me down at the track

SX has won me 7 national events, xc one, and the engine was toast after that event.........

XC engine has spent most of it's life in parts trying to figure why shit has failed..... I'm well over it...... record has been 17 hrs.....

5hrs, crank failure, $5k pro built engine based on brand new zero hours motor...... scrap......
Replaced cases, replaced crank, relined cylinder etc, 10hrs, top end went out of round cylinder, 2 to 4 thou out of round rattling like hell
replacement less than 1 hr on top end, didn't leave the shop it was so noisy, out of round cylinder liner .... over 2 thou out off round from 3 by 10 - 15 minute heat cycles, it was so damn noisey..... threw that one in the bin..... junk part......
Whole new top end, less than 1hr, cracked cylinder liner, turned out that the wrong liner was fitted, paper thin....... vendor replaced that part...... never coffed up for the piston that was wasted.....
Another complete fresh top end did 17 hrs, broke timing chain, top end way out of round by up to 7 thou ........
so yet another whole new top end + new crank + plus fresh bearings throughout as a precaution.... 3 years and only 34 hrs...... well sick of it..........

current rebuild is about detuning it for reliabilities sake....... LOL if an 807 cam can be though of as a detuned part !!

SX just keeps going, and goes damn hard..... can honestly say that I wish I had bought a second SX........... any more engine hassles and an SX will be going into it ! actually have a whole spare SX donor engine that will getting the once through as a race ready back up........
 
#18 ·
sorry for the rant guys, this things has exhausted my patience, it goes like a rocket, just wish it would hang togther a bit better..........
 
#20 ·
No need to be sorry for rant Kiwi, all great info to me, and I had not realized you had seen that much trouble with the xc's. I am thourghly surprised I have not seen any of these issues and I have done nothing to motor since new except some jetting in carb. And road the thing like I stole it. Still seems to be running strong to this date. The one other thing we had to do was replace muffler which was replaced with muzzy's muffler which seemed to give the machine some more torque as well as seems to rev better. Still not doubting anything ya have to say about them either. Keep up the great info. Look forward to reading about it.
 
#21 ·
that XC sounds just like my 06 yfz. I went through 7-8 motors in it. It turned into project quad, 06 cbr 600rr motor in it now that has yet to be finished, going on 5 years now lol. My built 540 is running great. Probably 80 hours on it and runs awesome still.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top