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-   -   Brison 6.4 question (https://www.rcuniverse.com/forum/gas-engines-142/8558547-brison-6-4-question.html)

thevirginian 03-09-2009 07:03 AM
Brison 6.4 question
 
Hey, guys. I had a little mishap over the weekend. While flying my 35% WH Sukhoi the motor came loose and rubbed against the baffle inside the cowl. Consequently the little linkage snapped off that connects the mechanical ignition advance ring with the bellcrank linked to the carb. I managed to fabricate a new one at the field, but had no idea what the exact length of that linkage was. After guessing the length the motor fired back up and ran fairly well. Was easy to start and transition was instantaneous. So was idle. But WOT I only could get 6100 with a Evolution 26x10. Anybody know how long that linkage needs to be? Any input is greatly appreciated.

rcdude7 03-09-2009 09:12 AM
RE: Brison 6.4 question
 

ORIGINAL: thevirginian

Hey, guys. I had a little mishap over the weekend. While flying my 35% WH Sukhoi the motor came loose and rubbed against the baffle inside the cowl. Consequently the little linkage snapped off that connects the mechanical ignition advance ring with the bellcrank linked to the carb. I managed to fabricate a new one at the field, but had no idea what the exact length of that linkage was. After guessing the length the motor fired back up and ran fairly well. Was easy to start and transition was instantaneous. So was idle. But WOT I only could get 6100 with a Evolution 26x10. Anybody know how long that linkage needs to be? Any input is greatly appreciated.

To get the timing right you are going to have to time it like it was new. You will have to find TDC and then adjust the timing link length for 28 degrees total ignition advance at full throttle. This is the only way to get it right, anything else is just a guess.

thevirginian 03-09-2009 11:11 AM
RE: Brison 6.4 question
 
Hey, rcdude
I thought I could short cut that step by asking what the exact length should be:). I wasn't sure either what the ignition advance for my engine is. You are sure it is 28° for the Brison 6.4, correct? I certainly appreciate your help.

rcdude7 03-09-2009 11:36 AM
RE: Brison 6.4 question
 
28 degrees total advance is generic for all gas two-stroke model engines, you can go slightly more but it will not incrase power much and you run the risk of detonation. 28 is safe.


If you have never timed the ignition before, here is a good description of how it's done. This is how I time my C-H converted G-62's


http://www.ch-ignitions.com/CHinst.html


Mike

thevirginian 03-09-2009 12:43 PM
RE: Brison 6.4 question
 
Thanks again. Yes, I do have this manual from CH.

CK1 03-09-2009 07:14 PM
RE: Brison 6.4 question
 
edited post

CK1 03-09-2009 07:16 PM
RE: Brison 6.4 question
 
thevirginian, rcdude7 has offered solid advice . Follow the instructions from C&H and set the timing by adjusting the length of the rod . I have 2 Brison 6.4's and the rods are not the same length . A static length check does not insure correct timing ,it has to be checked and adjusted. I also checked my 3.2 engines and none of them are exactly the same either.

thevirginian 03-10-2009 07:20 AM
RE: Brison 6.4 question
 
Thanks, CK1. That's exactly what I afraid of. That no linkage is of the same length. Oh well,[:o] I guess I will have to do it the hard way.


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