Rev 3 Timing?

[mcman56]

Is there a standard timing setting for the Rev 3?

I recently had a stator issue and had it rewound. First ride out was OK but soon was knocking. I raised the needle all of the way and it seemed OK. Third ride out and there is still a little knock when chopping he throttle. I'm wondering if I may have advanced the timing a bit..or if the rewind could have altered geometry slightly. Prior to rewinding the stator, I had the carb apart several times so I could also have unknowingly changed the float height. I thought I would look at the stator first. Overall, the bike runs good....soft but it is a 200. It will start from cold and idle with no choke so I don't think I have an air leak. (90 degree F)

[mcman56]

Wow...no info. I pulled the rotor off and the key was quite mangled so that may have been my issue.

While I was there, I looked at timing. I found a picture on line showing a 7.5 mm dimension. Mine was at 5.1. As a compromise, I went to 6.5. I also marked the flywheel for TDC. At 6.5, I got around 10 to 12 degrees of advance (using a timing light) That seemed low so I went back to 5.1 and got about 15 to 17. I'll try test riding with that.

For comparison, I looked at the all informative Sherco manuals. The stroke of a 2003 is within .5 mm of the Beta but I don't know about rod length. Assuming they are similar, the 3 mm setting would be 20 degrees of advance.

Does anyone have timing specs in degrees for other modern trials bikes?

[copemech]

Wow...no info. I pulled the rotor off and the key was quite mangled so that may have been my issue.

While I was there, I looked at timing. I found a picture on line showing a 7.5 mm dimension. Mine was at 5.1. As a compromise, I went to 6.5. I also marked the flywheel for TDC. At 6.5, I got around 10 to 12 degrees of advance (using a timing light) That seemed low so I went back to 5.1 and got about 15 to 17. I'll try test riding with that.

For comparison, I looked at the all informative Sherco manuals. The stroke of a 2003 is within .5 mm of the Beta but I don't know about rod length. Assuming they are similar, the 3 mm setting would be 20 degrees of advance.

Does anyone have timing specs in degrees for other modern trials bikes?

I can only give you a rough guide, as I set my bike to taste, and the numbers are all screwed up. It will drive you nuts!

If you have a standard referance point or mark, use that as a base.

Due to the diameter of the stator plate, each mm of rotation will roughly equal 1 degree of advance or decline from the basic point. (Think I calculated 1.12 or something at one time)

In retard, it normally takes about 2mm rotation to make a noticeable change in performance, while in advance(factory chosen balance), it only takes 1!

I would not pass 3 of these steps in either direction(2 in advance), less you may encounnter issues related to either extreme.

[mcman56]

Copemeh

What happens when you go to far? Does it knock like crazy on advance..or? I think I went 6mm in retard on my 2.9 and it made it a softy.

[copemech]

Copemeh

What happens when you go to far? Does it knock like crazy on advance..or? I think I went 6mm in retard on my 2.9 and it made it a softy.

Yes it will, as that is the third step of 2mm changes, and yet seems to run OK, but much slower. Seems if you go beyond that the exhaust gets too hot(too much uncumbusted fuel downstream).

On the flip side, more advance may induce greater kickback and stalling, not chugging slow well, and usually will not rev out as high. Depending upon the programmed advance curve, it may have a bit more mid, but? And yes at some point you get into preignition concerns.

It is all a tradeoff!