timing the cams

motoddrob

motoddrob

Hero member
Location
S/W Australia
I've just checked the inlet cam and found it 7? retarded. It'a a Axtel on A11 wheels.
My trusty calculator tells me I need to slot the flange 3.3mm to achieve 7?
Does that sound about right?? Phil,Piet, Keith, Red, anyone? Is there enough room on the flange to slot 3.3mm??
Haven't checked the Ex yet, I bet they're out!
Cheers
 
Rob,

Should be just enough metal there, but can be tight depending on the flange.  Some were drilled awfully close to the edge as standard, some cam blanks seem to have been a little dislocated on the cam grinder for final finishing.  Might be easier to drill and tap a couple of holes in the sprockets at the correct position.

piet
 
G'day Rob

Are you talking crank degrees or camshaft degrees?

As a rough rule, slotting the hole by 1mm will give a shift in valve timing of 40 at the crank

So a 3.3 mm slot will give you about 6.60 at the camshaft or 13.20 at the crank.

There's also another option with A11 cam sprockets. Unlike the 4C sprockets, the A11's have the bolt holes slightly offset from a tooth, so flipping the sprocket over may give you a closer fit to the desired timing and you won't have to slot the cam flanges out so much.

Cheers,
Camshaft
 
Hey Cam, good thinking batman!!, forgot to factor in the half speed of the cams. So 7? at the crank is only 3.5? on the cam then.
I'll try flipping the wheels then, otherwise as is, I'll need a ~1.75mm slot then. Correct me if I'm wrong, being dumb and all!!
Maybe I should read Phil's instructions again on the Lavermania site. I did read them several months ago, time to revisit.
 
The exhaust cam is 3? retarded at the crank and after remeasuring the inlet I've decided it's 10? retarded, measured at M/lift.
Measuring the max lift the inlet is .355", ex .345", which is less than the cam spec of 9.24mm
So 5? = 2.4mm slot,  1.5? = 0.71mm slot. Will try flipping the cam wheel first though.
 
Mine were 13 deg retarded inlet and 3 deg advanced exhaust. The PO had installed 4C cams with A11 sprockets. Fixed it by flipping the inlet sprocket and a little bit of hole slotting in the cam flanges. Made a huge improvement to fuel consumption and gained about 4 RWHP on the dyno.

Cheers,
Cam
 
So I've slotted my ex cam flange .72mm to advance the cam 1.5?
The Inlet cam needs to advance 5?, equates to 2.4mm. The original hole drilled in the flange is already off centre so slotting is out .
No worries, drill 2 new holes, got taps from 3mm to 24mm, bugger no 7mm!!
Looking at it and thinking too much, if I was to drill new holes 90? to existing holes, would I use the centre line of the bolt holes or the TDC mark as a datum in relationship to the teeth?? I measured the angle 14.5? C/L hole to TDC mark. So TDC should now measure 19.5?.
Thought about moving one tooth then work back, correct me if I'm wrong but 1 tooth equals 12? less 5, 7? equates to 3.3mm, still to much to slot the flange.
So I figure using the TDC is datum, advance the cam 19.5? and drill and tap the corresponding holes in the wheel.
I had ago at flipping the wheel but that made it worst, there was an ever so slight overlap on the #2 piston/valve :o Got to remember they're not flat top pistons!!
In hindsight, I could flip the wheel again and advance it one tooth and measure that, another option!!
Time to stop thinking and go to bed, it's 2am!!
 

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motoddrob said:
So I've slotted my ex cam flange .72mm to advance the cam 1.5?
The Inlet cam needs to advance 5?, equates to 2.4mm. The original hole drilled in the flange is already off centre so slotting is out .
No worries, drill 2 new holes, got taps from 3mm to 24mm, bugger no 7mm!!
Looking at it and thinking too much, if I was to drill new holes 90? to existing holes, would I use the centre line of the bolt holes or the TDC mark as a datum in relationship to the teeth?? I measured the angle 14.5? C/L hole to TDC mark. So TDC should now measure 19.5?.
Thought about moving one tooth then work back, correct me if I'm wrong but 1 tooth equals 12? less 5, 7? equates to 3.3mm, still to much to slot the flange.
So I figure using the TDC is datum, advance the cam 19.5? and drill and tap the corresponding holes in the wheel.
I had ago at flipping the wheel but that made it worst, there was an ever so slight overlap on the #2 piston/valve :o Got to remember they're not flat top pistons!!
In hindsight, I could flip the wheel again and advance it one tooth and measure that, another option!!
Time to stop thinking and go to bed, it's 2am!!
Click to expand...


Hey Rob you haven't tried swapping inlet and exhaust sprockets yet.

                                                                                  Dave
 
Rob, rather than trying to figure it out with maths and geometry, give this a try. Position the crank at the right spot for max lift, take out the camshaft sprocket bolts and tweak the cam to where it should be, then move the sprocket around a few teeth to get a fresh spot to drill some holes, and mark where the new holes should be. Takes all the head-scratching out of it.

Cheers,
Cam
 
This is interesting I was wondering can cam timing be a problem with standard 180 Jota`s using the original cams and sprockets

Kind Regards
Tetley
 
Even the Jap bikes which are known for precision engineering and high manufacturing standards are usually off. My 1988 CBR600 and 1990 ZXR-750 were way off. The Kwacker's lobe centers were off 13 degrees on the inlet and 10 on the exhaust side just to give an example (still in my archives, just had a look). For street use they were perfectly fine but as I was using the things as race bikes I took the time to dial them in properly. Our C4s and C7s do need to be set up properly to get the full benefits. The A11s will always work fine. Like anything they'll work best when the timing is correct. Probably the cheapest tuning to do too. If you can do this yourself then great. If you want to pay somebody to do this for you if you can't is also fine. Otherwise I wouldn't worry about it.

Tom
 
That's a good idea Cam, I'll do that to double check my new hole locations before drilling. I've just ordered a set of 7X1mm taps, coming from UK it'll be at least a week before they show up!! Called a few of my well equipted tool mates around here to see if anyone has a 7mm tap, no luck, seems that 7mm arn't included in most tap and die sets. Living in bum fuck nowhere has it's disavantages when you need specialized stuff.
 
The only other mfgr's I've run across using 7mm stuff have been BMW,Alfa[old,60's-70's] and I think Mercedes. You might try a friendly dealer mechanic and see if they could tap your hole.[Pun intended]
 
Vespa uses 7mm a lot, and Italian and French high-end bicycle components do too. A pro bicycle shop would have them.
But oddly enough I've bought a couple of cheap Chinese tap and die sets, and they both had M7 taps, although taper only. Although I only use them to chase holes, I bought proper ones for new work.

Ken
 
wdietz186 said:
The only other mfgr's I've run across using 7mm stuff have been BMW,Alfa[old,60's-70's] and I think Mercedes. You might try a friendly dealer mechanic and see if they could tap your hole.[Pun intended]
Click to expand...

Well the nearest civilization is 120 kays away so no dealers but we do have a local mechanic. I'm not in any hurry as I still have shit loads to do on the frame,wheels,brakes, electrics, carbon panels and then paint. I'm keen to get the motor finished so it's sealed up and ready to go. While waiting for the taps to arrive I can keeps moving forward with the carbon.
Also have a paying job I've been neglecting and my client is asking when it will be finished so need to get that out of the way too, so sometimes it's good to be waiting for something so I can get on with all the other day to day tasks that need doing when living in the bush.

Ken, lots of 7mm taps out of china on ebay, cheap too, but I brought out of UK hoping it will be a quality product, doesn't mean that it's not from China though!! I brought a set of 3.
 
mcnicol said:
Cam, if you do that, what do you use to hold the cams still while you wiggle the sprocket? Vise grips? (serious question, I'm interested in trying it)
Click to expand...

Yep. Vice grips work well if you want to hold onto the camshaft. But you probably won't need them in this instance. With a cam lobe at maximum lift, the valve spring isn't trying to push it either way because it's dead centre on the lobe.

Cheers
Cam
 
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