R60/5 pinking ... (with a parts request)

[StephenB]

This has been covered before many times ...

I am building up this 60/5 engine from parts and am aware of its tendency to ping under load. Since I'd like to stick with the points ignition (maybe only adding a Dyna Booster to it) I looked at potential ways of helping avoid pre-ignition and not loosing the high compression or dual-plugging and electronic ignition. One part of this equation is using a '77/'78 advance mechanism which is different from the /5 ones: it obviously starts to advance later @ 1800rpm (heavier weights?) but still maxes out at 3200rpm (softer springs?). Makes sense to me.

Anybody on the board have such a '77/'78 advance with springs and weights that s/he may consider to part with as you'll never use it again? I can trade for a original R75/5 mechanical advance or buy it outright.

[Garnet]

A freind had a 1977 R60/7 that had had the compresion lowered by a PO. I can only asume it was to reduce the pinking, but we never tried it with the stock compresion so I can't be totaly sure.

My favorite R60/5 was OK with points and high comp as along as I ran 94 octane gas.

Edit:

How about heavier advance springs? On 91 gas my bike was fine above 4000 rpms. Perhaps slowing the max advance to a higher RPM would help.

[chasbmw]

I know that you did not want to go electronic, but the Boyer ignition curve was set up to knock back the timing between 2500 to 3000rpm with the specific intention to reduce ping on the 600s.

Given that they pinged on the good quality high octane gas available in the 70s, without compression plates, I think that you might have some difficulty. I wonder why the 600 was so prone to pinging? The size of the bore, or was it the slide carbs?

Charles

[Garnet]

Given that they pinged on the good quality high octane gas available in the 70s, without compression plates, I think that you might have some difficulty. I wonder why the 600 was so prone to pinging? The size of the bore, or was it the slide carbs?

Charles

I believe it has to do with either combustion chamber shape not matching the pistons in the squish band, or the compresion ratio not matching the 296ish stock cam.

I would love try a 308 cam from the bigger bikes in 600. By leaving the intake valve open a bit longer the effective compression ratio is lowered at lower RPMs, right where the pinging of the 600 is the worst.

[StephenB]

Edit:

How about heavier advance springs? On 91 gas my bike was fine above 4000 rpms. Perhaps slowing the max advance to a higher RPM would help.

That is a possibility too, but I like the /6/7 solution better. Makes more sense to me.

Charles, I do have an single plug EI that I can throw in and it will most probably work. But I like the challenge

[mattcfish]

This has been covered before many times ...

I am building up this 60/5 Since I'd like to stick with the points ignition (maybe only adding a Dyna Booster to it) I looked at potential ways of helping avoid pre-ignition and not loosing the high compression or dual-plugging and electronic ignition. .

What??? Not an Omega?

I've also wondered what a 308 cam would do for these bikes. That and lightening up the top end and valve train, clutch, flywheel and ...the whole bike. Make a Boxer that revs. I've got a spare 60/5 case in the garage. I noticed that you can't put a 336 in it without modifying the length of the lifter channels. The lobes hit. The 308 fits just fine. Just in case anyone wanted to know.

[Major Softie]

I've also wondered what a 308 cam would do for these bikes. That and lightening up the top end and valve train, clutch, flywheel and ...the whole bike. Make a Boxer that revs. I've got a spare 60/5 case in the garage. I noticed that you can't put a 336 in it without modifying the length of the lifter channels. The lobes hit. The 308 fits just fine. Just in case anyone wanted to know.

Beginning to sound an awful lot like an R65...

[Garnet]

I have been in Winterpeg visiting the outlaws for the last few days, and that has left me with a few moments to reflect on life. Sadly all that has come to mind is how to make an R60/5 stop pinking, I realy do need to get a life.

How about retarding the cam timming? General accepted practice is that for every 5 deg of crank rotaion that the cam is retarded the maximun torque moves up about 300ish RPMs. Most cams will not tolerate much more than 10 deg of change either side of design, before they begin to loose their designed performance. The milder cam the more wiggle room.

The theory here is, to close the intake valve a bit later, perhaps closer to where a 308 cam closes. This lowers low RPM real compresion (and power) and should help reduce detination at lower RPMs. The engine will feel a bit more slugish up to 3500ish RPMs but will have a tiny bit of a kick around there as intake forces balance out and the cylinder begins to fill more completly. A stock R60 type 247 has a very flat torque band and pulls evenly throgh the RPM range, this will make it feel a bit more "cammy" with more willingnes to rev above 4000.

It costs no money to try, just some time. To retard the cam, leave the woodrof key off of the crank when installing the timming spocket onto the crank. It is just there for timing purposes, the sprocket is held in place by an interfeance fit. With the sprocket at about 300 degF you have about a full second after you drop it on the crank before it grabs. I have done this a couple of times on Classic Era engines and not had the spockets move over time.

You can carefully mark the crank with a degree wheel, but the width of the keyway is about 10 degrees.

The only snag here is to consider igntion timing after the cam has moved. If you go as far as 10 deg you may have to elongate the slots in the points backing plate to get the points opening (or electonic ignition trigering) at the right spot. With a crank trigger it doesn't matter.

Some reading on how to use a degree wheel:
http://www.cranecams.com/uploads/instructions/803.pdf

I have some more stuff on my computor at home which I will add.

[mattcfish]

I have been in Winterpeg visiting the outlaws for the last few days, and that has left me with a few moments to reflect on life. Sadly all that has come to mind is how to make an R60/5 stop pinking, I realy do need to get a life.

How about retarding the cam timming? General accepted practice is that for every 5 deg of crank rotaion that the cam is retarded the maximun torque moves up about 300ish RPMs. Most cams will not tolerate much more than 10 deg of change either side of design, before they begin to loose their designed performance. The milder cam the more wiggle room.

The theory here is, to close the intake valve a bit later, perhaps closer to where a 308 cam closes. This lowers low RPM real compresion (and power) and should help reduce detination at lower RPMs. The engine will feel a bit more slugish up to 3500ish RPMs but will have a tiny bit of a kick around there as intake forces balance out and the cylinder begins to fill more completly. A stock R60 type 247 has a very flat torque band and pulls evenly throgh the RPM range, this will make it feel a bit more "cammy" with more willingnes to rev above 4000.

It costs no money to try, just some time. To retard the cam, leave the woodrof key off of the crank when installing the timming spocket onto the crank. It is just there for timing purposes, the sprocket is held in place by an interfeance fit. With the sprocket at about 300 degF you have about a full second after you drop it on the crank before it grabs. I have done this a couple of times on Classic Era engines and not had the spockets move over time.

You can carefully mark the crank with a degree wheel, but the width of the keyway is about 10 degrees.

The only snag here is to consider igntion timing after the cam has moved. If you go as far as 10 deg you may have to elongate the slots in the points backing plate to get the points opening (or electonic ignition trigering) at the right spot. With a crank trigger it doesn't matter.

Some reading on how to use a degree wheel:
http://www.cranecams.com/uploads/instructions/803.pdf

I have some more stuff on my computor at home which I will add.

According to Snow Bum, you have to double the advance or retard on the cam because it turns at half the rate of the crank. My late 336 cam that is 3 degrees advanced at the keyway is actually 6 degrees advanced (according to SB).

[chasbmw]

Would it not be easier just to slot in a 308 cam? Must be lots available cheap second hand?

Possibly not so much fun, but if the cam timing is causing the pinking then is this not a pragmatic solution?