79 SRX Tuning Help

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PacAttack

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Feb 20, 2006
Messages
4
Location
Warren, MI
Long time reader first time poster
Looking for some tuning help from the SRX experts

I've been a huge fan of the SRX's for years and was in the process of restoring my 1st 79 and adding to my collection when I came across another great low milage low unit in Indiana back in mid January (1035 original Km on her)

I installed in her the fresh rebuild I had just put together for my resto project with relined stock ported cylinders (nikasil), fresh seals, new pistons, rings, gaskets, the works. Timing set with dial indicator to factory settings. Carbs cleaned and all jets and settings put to factory specs. Comet 102c primary with about a 5000 RPM engagement.

I build this sled to be a reliable trail sled to ride in vintage events. I actually just ran it 155 miles in the "vintage challange" ride in St. Germain, WI during the Hall of Fame "Ride with the Champs" last weekend. Only Yamaha out of 26 vintage sleds to try it. Only 23 came back, and I was barely one of them.

With all of that said, how do I get any low end performance out of this thing?
Anything below 6000 RPM's it won't get out of it's own way once the engine comes up to opperating temp. I've played with a lot of different sleds over the years, and usually at factory things will run fairly well. I know these are high strung little monsters, but I'm wondering where to start with the tuning. To me it's just way to rich and the plugs indicate the same thing.

Sorry for the long message, anyone got any ideas?
 

I have a 78 and have the samething. It is very bad below 6000 but I think this thing would run all day at 60mph and be very happy.It will eat a belt in a day(yes the clutchs are alined) I have tighen up the driven and this helped but it suck the gas.Mine is all stock to and new cyl. maybe someone can help with this ?
 
When it gets hot - take the air box off - and see if that improves low end - if it does changing the slide or maybe changing the needle position would fix it.

Don't run at wot the the box off.
 
ITS ALL IN JETTING. GREAT START CHANGEING NEEDLE POSITION. BUT TO DO THIS RIGHT, THE WHOLE CARB SYSTEM HAS TO BE LEANED. ANOTHER WORDS, DROP PILOTS, CHANGE SLIDES, AND BRASS. ALSO BLOCK OFF POWERJET AND USE ONE MAIN JET ONLY. RUN ATLEAST 5000 ENGAGEMENT. YOU WILL NEVER GET IT 100 % BUT IT WILL BE BETTER. 3:16 (yammie tony)
 
Thanks Yammie God 3:16, I apprieciate the advice.

I figured it was all about an over jetted situation.

Suggestions on where to start with the jetting on a stock motor? Pilots, how far? Brass?

By dropping the power jet out, what size would the main have to go to?

This whole power ject carb set up is foreign to me, I've played with a lot of round and flat slide Mic's.

Any experieces and guidance would be great.

Ross
 
ROSS , I CAN GIVE YA ALL CARB SPEC,s BUT FIRST I NEED TO KNOW WHAT CARBS ARE ON THIS SLED. STOCK WAS .36 mm POWERJETS. 3:16 (yammie tony)
 
Yammie 3:16,

They are the stock 36mm '79 carbs- 340 mains- 80 power jets and 30 pilot

Thanks for the help,

Ross
 
THATS WHAT I NEED TO KNOW.
STAY WITH A 30 PILOT, BUT CHANGE NEEDLE POS TO FIRST NOTCH. DROP MAIN JET DOWN TO A 310. IF POSSIBLE SEE IF YOU CAN FIND A 2.0 SLIDE. ALSO TURN YOUR AIR SCREW OUT ANOTHER 1/2 TURN. THESE CHANGES SHOULD HELP CLEAN UP THAT LOW END. LET ME KNOW. 3:16 (yammie tony)
 
Is there anyone else here who has a 78 that run like this? The stock carb set up on a 78 is310 main 30 pilot and the needle and needle jet are different from a 79 but mine run like this
 
JDlefturn said:
Is there anyone else here who has a 78 that run like this? The stock carb set up on a 78 is310 main 30 pilot and the needle and needle jet are different from a 79 but mine run like this
Click to expand...
THATS CORRECT, THE 78 SRX JETTING WAS SLIGHTLY DEFFERENT THAN THE 79. 3:16 (yammie tony)
 
PacAttack do you think that if we changed the jet needle or needlejetand leaning it out a bitt. Because mine starts and idols fine and top end is good.the 79 needle and jetneedle are diffrent then the 78
 
Pipes

The 76's are the ones with different pipes but look real similar to th 78-80's.
 
The 1980 SRX pipes are different than 1978-1979. The pipe difference is minimal but less performance from the 1980 pipe. Trust me, I have cut 1978, 1979, and 1980 pipes apart.
 
1978-79-80 SRX PIPES ALL HAVE SAME PART # 8G9-14610-00. THE MAG PIPE ON THE 80 SRX HAS DIFFERENT PART NUMBER. INTERESTING. 3:16 (yammie tony)
 
All these srxs 78-80 bogged out of the hole, you had to have the engagement way up on them.turn the carb idle up and notch or flat cut the clutch arms, which should be N-1 arms to bring up engagement. put a orange -black primary spring (170-300) from wahl brothers part number 07-376. then hang on. These sleds were not much for trail riding but were a blast on the lake.
 
ENGAGEMENT SHOULD BE ATLEAST 5500. GREAT POINT. ALOT OF IT WAS CARBERATION BUT SOME OF IT WAS IN THE BELT CENTER TO CENTER SPEC ALSO. ESPECIALLY WITH THE COMET CLUTCH. N-1 WEIGHTS WORKED REALLY GOOD. 3:16 (yammie tony)
 
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