[Dirttrack33]

I have a 1978 xr75 with scored journals on the head, Cam is also spent. Will a 1980 xl80 head and cam interchange onto the '78 engine? Looks visually close but don't want to make a pricey mistake.

 

[firepower354]

Yep. Compression may be slightly lower, and fins bigger, but it's a bolt-on. Cam from the 100 has a MM more lift, too, adding a bit of top end performance.

 

[AHRMA361]

Can't remember which, but XL heads also have a head stay mount on them that the XR's don't (the 100's do for sure....maybe the 80's dont....code on head is 152). The XL head is a drop in like FP said.....go with a 100 cam or buy aftermarket and add a pipe and carb w/opened up airbox for good performance, if that is what you are looking for.....

 

[firepower354]

Head stay on a 75/80/100 series? I thought the old 100/125 jobs were all with one? Old guys lol

 

[Dirttrack33]

Thanks for the replies. I will be tearing down the xl this weekend, fingers crossed that the head is in better shape. If memory serves, that engine jumped time so likely bent valve but hopefully no scoring.

Question on the 100 cam - will a stock cam from a 2004 crf100 fit? I upgraded my 100's for at-home flattracking and have two stock cams sitting around.



The xr75 will be a rider, want it nice but not restoration-quality. I'm also working on a 1975 xr resto project but not finding the parts I need at a reasonable price so it sits... So many projects and so little time.



Terry, I'm the guy who traded you the xr100 engine for the Pitster parts last year - man, that bike is fun!

 

[firepower354]

lol. Haven't touched the engine, except to slide it around on the shelf looking for stuff



100 cam will work nice in a 75/80. 1mm more lift.



What 1975 parts?

 

[Dirttrack33]

1975:nicer set of fork legs, decent tank and a new set of rims/spokes. 1978: one non-pitted fork leg, perches and lever covers (used ones) to give it some semblance of oem. Could also use a reasonably servicable stock pipe.

 

[firepower354]

Mike at TB had a few NOS pipes. The rest should be pretty ea$y.

 

[Dirttrack33]

Have you got any of the used stuff I mentioned?

 

[firepower354]

Nah. My old stuff was junk.

Rear rims are available new, cheap, I think. Aftermarket for spokes.

 

[AHRMA361]

Head stay on a 75/80/100 series? I thought the old 100/125 jobs were all with one? Old guys lol

Absolutely! The first version XL's to not use the old-style (SL/CL/CB) 100 engines, I think in 1979-80, maybe 81 as well, had a cast in head stay lug to tie it into the frame....I may be old, but.....err, uhh....what was I gonna say?!



Oh yeah! That I can remember stuff....sometimes, well, alright, occasionally!!

 

[firepower354]

Yeah, that's what I'd meant. the head-stay versions won't bolt to any XR or other 75/80/100 series "small block" upright

 

[Dirttrack33]

ok, thanks anyway. Could you give me contact info for the guy with the pipes?

 

[AHRMA361]

Yeah, that's what I'd meant. the head-stay versions won't bolt to any XR or other 75/80/100 series "small block" upright

No, What I meant was the 79-85 XL100S Honda head HAS A HEAD STAY.....and, bolts on later XR/CRF100/80 cylinders.......check the fiche....you, you, you,....non-believer!!! lol



patiently awaiting the crow for lunch bro....ha!

 

[firepower354]

And just as I'm so tired of turkey...

I suppose it might be OK, smothered in BBQ sauce, but Mandy's gonna be pissed about having to pluck & clean it.