New digital CDI for RD500 available

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wolfgangh · #31 Post by **wolfgangh** » Sun Jan 07, 2007 5:32 pm

If I time it off the rear cylinders with the TSI spec ignition curve (= +5deg on stabdard curve) with max. 34 deg BTDC @ 3500 RPM, I would get 35,5 deg max @ 3500 RPM at the front cylinders then..isn

wolfgangh · #32 Post by **wolfgangh** » Sun Jan 07, 2007 5:37 pm

Jeff, do you mean you machined an offset key for the crank gears to bring them in perfect sync or an offset key for the rotor to adjust ignition timing but leave cranks out of snyc?

#33 Post by **smurph** » Sun Jan 07, 2007 5:50 pm

I think Jeff was talking about the cranks. Making both cranks hit TDC at the same time.

I don't know about a stock engine with Yamaha pistons. Never measured one. But as soon as you drop pistons in with/without wrist pin offsets, you will get the timing variances between the two cranks. This needs to be corrected and Jeff knows the way.

Now, if you are going to use the multiple input triggers on Borut's CDI, then you will not have to worry about the crank timing so much. But you will have to fabricate a VR sensor onto the rear crank. Not so easy to do since there is no crank snout on the rear on most bikes. My thoughts were to use another lower/front crank in the upper/rear and make a seal to replace the standard plug. The seal could be made from a lower stator side crank seal (same as RZ/RD350) and an aluminum adapter bushing. In fact, this is how one of my engines is being built right now.

But Jeff's method is easy. I used to build offset keys for Briggs and Stratton engines before they became readily available. Same principle.

Steve

#34 Post by **rztom** » Sun Jan 07, 2007 11:13 pm

Hey Steve.... where'ya been... on holiday..

cbn70 · #35 Post by **cbn70** » Sun Jan 07, 2007 11:51 pm

So is it a common problem for the rear cylinders to be out 2.5 degrees? Then is the standard fix to use an offset key to fix the problem? There is no problem with the key shearing off?

Chuck

#36 Post by **hybrid** » Sun Jan 07, 2007 11:56 pm

smurph wrote: Now, if you are going to use the multiple input triggers on Borut's CDI, then you will not have to worry about the crank timing so much. But you will have to fabricate a VR sensor onto the rear crank.

Or you can use an ECU like mine that has two separate ignition curves and allow for the 2.5 degrees in the rear banks ignition curve

#37 Post by **smurph** » Mon Jan 08, 2007 1:58 am

rztom wrote:Hey Steve.... where'ya been... on holiday..

Yeah... more like a whole bunch of work! They have been killing me lately. But I did manage to get some good quality time in on the stock 500 engine. All machine up and ready to put together. I'm going to paint it first, that's the holdup.

cbn70 wrote:So is it a common problem for the rear cylinders to be out 2.5 degrees? Then is the standard fix to use an offset key to fix the problem? There is no problem with the key shearing off?

I would say it is a very common problem. Just not commonly known or dealt with problem. If you look through the archives, you will see several mentions about using different pistons, mostly wisecos, and their associated pin offsets. Not pin height, mind you, but pin offsets in relation to closer or further away from the exhaust port. I'm not sure of this, so don't hold me to anything, but I believe the wiseco 236 has the correct pin offset for the lower cylinders. The problem is that we turn these guys around and use them in the upper cylinders but the cranks turn the same direction! So if the offset is .005" and is correct for the lowers, then the upper offset is off by .010". Enough to bring to light the crank timing differences to the discriminating builder.

As I mentioned above, I'm preparing to put one of my engines together and I will see what gives. But I have already planned on making an offset key and bought some 4340 stock to machine it out of. I really doubt that there will be any shearing problems. But if one was worried about it, you could machine it out of S7 and heat treat it.

hybrid wrote:Or you can use an ECU like mine that has two separate ignition curves and allow for the 2.5 degrees in the rear banks ignition curve :Cool

Yeah, I'm envious of your beta MicroSquirt.

You are going to have some fun with that. You will have total control over all aspects of your engine. But... along with flexibility comes complexity. Don't give up on it. Just get a bigger hammer when needed.

I wish I could be there when you are firing it up so that I could see the grin on your face!

Steve

#38 Post by **hybrid** » Mon Jan 08, 2007 3:23 am

Maybe I will video the big day and post it up for all to see

wolfgangh · #39 Post by **wolfgangh** » Mon Jan 22, 2007 5:05 pm

Finally started my engine first time,with Boruts programmable CDI and PV controller. These units are really great and very easy to program. Turned out that the default values for 34 deg static angle and 30us compensation are almost spot on.
I did not ride the bike nor did I have it on a dyno, just let it run through a heat cycle first time. After fully turning in the pilot screw , engine response was perfect, so will increase pilot jet ("slow jet") of my PWK carbs by 2 sizes or so.
Always again a great feeling when a new engine runs first time!

I have NO BALANCER SHAFT but engine does not vibrate at all! Seems like Marco B