Valve timing

Keith, 1 degree with no chance of slipping would be great. But I don't have any way of drilling my sprockets to that level of accuracy, and I don't know anybody local that i could trust to get it right. I could send you my sprockets, or Vince in Sydney has his fixture, but that means sending bits of my bike off to the ends of the earth.
I rather suspect that there's more than a few others like myself who would stand to benefit from a simple bolt on solution that could be put back to original easily.
Plus racers and cam profile developers (Crispin/Ian/Steve and Scott, any comments on this?) could use this to change their cam timing quickly, don't need to take the cams off, just loosen a couple of bolts, reposition, retighten and you're done!

Ken
 
ken, what you are talking about should work for the 120, too
if, as keith points out, it can be made to fit

what it may come down to is whether the end user has the need
to dial the cams in quickly like one might if spending dyno time

a street bike or occasional track bike user really isn't going to be
altering the timing with any regularity. most likely set and forget

my own inclination is to consider sprocket blanks made to suit,
fully drilled and ready to install. lower per unit cost.

dealers have a lot of paid for inventory sitting on shelves
so stepping up to stock reduces available capital for fast moving items

you can get pretty damn close with basic tools
if you knows where the valve timing events are preferred
the full circle of holes is not required

cheers,
scott
 
I think I've mentioned this before - but with a simple bit of machining to cam pillars and head - the camwheels can be slotted to take nuts and bolts - makes cam timing and cam change a doddle - paying out a load of money on vernier or whatever sprockets does (to me anyway) seem a bit of overkill. I must have slotted about 100 sprockets and used the original 7mm bolts - yet to see one slip  - it's the surface area of metal to metal that holds things in position - not the strength of the bolts - Regards - Phil
 
Hi Phil, that's what I was planning to do if my cams needed dialing in at all. Can't wait to get my head back so I can get stuck into it, I'm all excited!!
 
mcnicol said:
Plus racers and cam profile developers (Crispin/Ian/Steve and Scott, any comments on this?) could use this to change their cam timing quickly, don't need to take the cams off, just loosen a couple of bolts, reposition, retighten and you're done!
Click to expand...

It's not quite that simple Ken, you can get valve to piston clearance problems when you alter the timing and it should always be checked after you alter the timing. I've got slotted cam wheels on my racer, no cost [other than a bit of time] , no clearance issues and micro adjustability with a proven reliability record. No point in over complicating things.... :D
 
just loosen a couple of bolts, reposition, retighten and you're done!

Hi Bob - It got that simple with my mods (adjusting a cam in situ)as i always retard the inlet and advance exhaust - keeps valve to valve (more likely on a triple) clearance wider - and always make sure the valve/valve clearance is adequate at std timings. - Regards - Phil
 
Just as a follow up on this old thread, I finally got around to putting my bike on the dyno yesterday to check what difference dialling in the valve timing made.

Other then much improved fuel consumption (mentioned in an earlier post) the dyno tells me that there is about a 4 HP increase right through the rev range, and the the A/F mixture has leaned out by about 0.5% (around 12.5% to 13%).

Peak RWHP went from 69.5 to 73.7. I dunno whether that's about average for a Jota or whether it's still a bit down on power.

I tried swapping the 125 (Dellorto) main jets for 120. It leaned the mixture off by another 0.5% but made bugger all difference to the power curve.

Cheers,
Cam
 
I have A11 cams and standard wheels on a 180 triple, with slots for adjustment and I'm timing the cams.

Exhaust is set to max lift at 96 degrees BTDC no problem.
Inlet I am aiming for max lift at 108 degrees ATDC, but I can only get to 111 degrees at the extreme of the slot. I have about 10 degrees of slot adjustment. If I move the chain by a tooth I'll move by 24 degrees (I think) so the 10 degree slot will not get me any closer than I am now.

As the slots were done by somebody reputable and waaaay more knowledgeable than me (but he only had the head so could not do the timing), should I get the file out and extend the slots by about 1mm or am I missing something?

Thanks

Matt

 
Thanks Phil. Inlet cam sprocket turned but I still need another 2.5 degrees - which is an improvement, but not there yet. Also I had to move the wheel by three teeth from the sprocket timing mark to get this close, which seems wrong to me.

Keith N did my slot (if you see what I mean) so I'm concerned that I'll make things worse rather than better if I slot the hole further. So before I remove any metal, my question is how long (how close to the edge) can the slots safely be?

Thanks

Matt

 
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