Yamato 302 & 102 Ignition Timing

[modifiedoutboard]

A new Racer emailed me regarding Yamato 302 and 102 Ignition Timing Specs

Yamato 302 stock ignition timing?
Yamato 302 Mod ignition Timing?

Yamato 102 stock ignition timing?
Yamato 102 mod ignition timing?

Can "anyone" help out?

RC Hawie where are you?

Scott Clark?

Anthony
Just another Race Boat Sponser

[roperz111]

Anthony,

I would suggest setting the timing on the 102 Stock ignition between 0.225" - 0.245" BTDC.

CJ
111-Z

[Dick Tyndall]

Actually, I'm the one who e-mailed Anthony about this. I am looking for the numbers for the exhaust opening, closing and duration............same thing for the cylinder intake ports. For example, on one of my R/C model boat engines, to check the exhaust timing I would install a 360 degree timing wheel and a pointer that would be set at "0" with the piston at top dead center ( ATDC). Rotating the crank in the direction that the engine runs, starting with the piston ATDC, the top of the piston would just to clear the top of the exhaust port. At this point the pointer would be pointing at 268 on the wheel. Still rotating the crank, the piston travels down and then starts back up until the top of it just reaches the top of the exhaust port. Looking at the degree wheel again, it is pointing at 92 degrees. By subtracting this number (92) from the first number (268) you get your exhaust duration, which would be 176 degrees.
I don't have a Yamato here (yet) to check this with and just thought someone out there in hydroland would have these numbers so I could compare these with my little engines.

Thanks for the info

[mercguy]

hope this helps ya Dick. I did post some info before, but seems Mr. Race Boat Sponser deleted it all.....what a chump.

[Dick Tyndall]

Thanks for the info, Daren.............looks like I have a lot to learn about Big boat racing motors.............

[modifiedoutboard]

Both of the Yamatos exhaust open/close close to 96 deg atdc, guess you are running pipe simulations.
Rod lengths, strokes, trans ports, etc..... are on the APBA mod spec sheet.

C mods are turning in the low 8,000 rpm range

hope to finally test a 102 pipe in the spring.

Anthony
Just another small Race Boat Sponsor

[Dick Tyndall]

Again, thanks for the info.........I'm starting to get a picture of what's going on inside these Yamato motors. With the 96 degree opening and closing number you gave, I assume this means the exhaust DURATION is at 168 degrees.............which is on the high side for a non-piped motor, but on the low side for a piped motor.
I would be interested to see how your 102 pipe test comes out, but without "throwing all of your cards on the table", give us enough to see what's going on.
Always nice to see racer's sharing their knowledge..........a plus in any sport.

[modifiedoutboard]

i found some stuff on my computer for the 102

inches mm
BORE 2.625 66.7
STROKE 2.288 58.1
ROD 4.21 106.9

Rod/Stroke Ratio 1.84 , consistent with modern 2-strokes.

For the 302

inches mm
BORE 2.625 66.7
STROKE 2.276 57.8
ROD 4.205 106.8

Rod/Stroke Ratio 1.85

Need to look at an actuall engine, the way the dims stack up with tolerances could put exhaust timing any where from 94 to 96
ATDC, RC Hawie knows!

Anthony
Just another small Race Boat Sponser

[mercguy]

Originally posted by modifiedoutboard
Both of the Yamatos exhaust open/close close to 96 deg atdc, guess you are running pipe simulations.
Rod lengths, strokes, trans ports, etc..... are on the APBA mod spec sheet.

C mods are turning in the low 8,000 rpm range

hope to finally test a 102 pipe in the spring.

Anthony
Just another small Race Boat Sponsor

I can hear it now...........a Yamato with "a pipe that works"!:(

[modifiedoutboard]

Grammarical error, the sentence below conveys the intended
meaning behind the previous post.

Hark! I can hear a Yamato with a pipe that works now.

Still alot of testing and some revisions before you hear the fat pipe sing!

[pro350hydro]

This thread started out asking for "ignition timing"

Since, it has changed in to asking about "port timing" numbers

and "who" is the motor builder here???

Looks like you got all the number you need now....

[modifiedoutboard]

Still needs Crankcase Compression, exhasust port dimensions,
intake info and some other paramaters