77 srx crank cases

sledcollector said:
what changes are made to put a 79 crank in a 77 motor ? what is the stock port timing specs for the 8f2 cylinders ? I have a 77 that won't run right ! I don.t know if it's been ported more than stock ? how far can you go ?where do you measure from / to ign. timing specs ? this ting runs like crap & it should haul ***. I don't know what the previous owner did but its all new ! pistons ,rings nikasil ,crank , all proper 77 ign. parts but no power jets. just 360 mains he had 480 in it y6 tubes &7f6 needles .It spits back fuel at low rpm .the closest to running half good was to move the stator all the way clock wise then it smoked the belt at engagment[ 6000 rpm ] drove out 100 ft then came to life 10,000 rpm max for 6 or 7 hundred ft any suggestions other than sell it.I want to run right before i restore it thanks Andre
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I'm no expert on mik's or srx engines,but no way i'd run a 360 main in my Gpx.My carbs came (38mm) stock with 360's and I pulled them and went up to a 450 worked down to a 400.
 
Thanks guys ,any help is appreciated ! the only reason i tried 360 mains is it was spiting fuel & it callsfor a 200 main & 160 power jet . but the power jet was taken out The timing is set @1.9 mm ,what #s should be on the stator, flywheel & box ? compression ? mine has 160 ! how do you identify a77 vs78-79 cases are they different ? let me know how the hewtech ign. works thanks Andre
 
this is the engine timing page from the 77 service manual, hope this helps and in the back of my manual in the memo page it had update timing specs as follows;0-32degrees-2.25mm B.T.D.C HEADLIGHT ON -40-0 DEGREES 2.25MM HEADLIGHT OFF IT ALSO HAD STOCK CARB UPDATE SETTINGS FOR POWERJET CARBS BUT YOU SAID YOU DONE AWAY WITH THEM hope this helps!
 

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I THINK I CAN HELP YA HERE, BUT RIGHT NOW I AM ALITTLE CONFUSED WHERE YOUR AT. IT SOUNDS LIKE YOU HAVE AFEW DEFFEREBT THINGS GOING ON. I WILL SAY who ever BLOCKED THE POWER JET AND RAN A FIXED MAIN WAS RIGHT. THOSE POWER JET CARBS WERE A NIGHTMARE. 3:16 (yammie tony)
 
Thanks guys! the pics you posted ramblnman ,shows afly wheel with 2 access holes , mine has three.Yamie god i'm trying to to see if someone changed things that will not work [crank ,cases, porting , ign., carbs ] i see some of the differences in the earlier posts, but are there #s on the cases or just the timing cover ,cylinders & head. Could someonehave put a 79 crank in it . Is the key way in the same location the exh. can has been cut & the insulation taken out 10 mm taken off of the head pipes as per the bulletin. [previous owner did this ] thanks again Andre
 
SHURE ANYTHING IS POSSIBLE, ALOT OF THAT SRX STUFF COULD BE MADE TOO WORK , OR HACKED UP. TELL YA THOUGH JUST SHOOTING OFF MY HIP HERE, ITS SOUNDS LIKE A HUGE PART OF YOUR PROBLEM IS CARBERATION. YOU REALLY NEED TO GO THROUGH ONE THING AT A TIME AND POST HERE WHAT YA GOT. SOUNDS LIKE YOU MIGHT HAVE A FRANKINSTEIN MONSTER THERE. KEEP IN MIND THE PREVIOUS OWNER MIGHT OF KNOW,IN WHAT HE WAS DOING IF HE FOLLOWED TECH BULLETIN,s!! 3:16 (yammie tony)
 
ok so we got it to run better! the coil had a bad plug wire but should'nt the timing move with the rpm ? .we set it @ 2 mm or .080 " , fired it up and at idle its at 2mm and at 7000 rpm , did not move still at 2mm. is the box bad ? we havent taken it off the jack stand but thedrive beltis in it. the carbs have been line bored and the top ridge of the needle tube no longer sits flush with the bore . it has y-6 tubes &7f6 needles with the clip in the second groove from the top . like i said it runs better but wont start without the choke . so we went from 30 to 85 pilots [i know this is way too big ] but we wanted to see if it would startbetter .and we still need to choke it we got the bulletin port spes and this motor was ported to those measurments. the pipes have been cut 10 mm & the insulation taken out of the can . i have c-14 v p fuel in it 112 octane . thanks again Andre
 
OK. I just had a brain storm. There was a sled a while back that wouldn't run worth a S^%t. Come to find out it had stock heads put on it when the guy bought it thinking that they where cut to match the full race porting. He was trying to run this on 144 VP fuel. It wouldn't burn the fuel. He had one hell of a time even getting it started. Mybe someone switched heads!!!!! What's the squeesh???? Dean-o
 
I MIGHT BE WRONG, BUT DON,T REMEBER ALOT OF ROOM FOR MORE PORT WORK ON 77 SRX CYLINDERS. I HAVE SEEN SRX CYLINDERS THAT WERE JUNK BECAUSE PORTS WERE HOGED TO WIDE. DEAN, HOW IS THAT FOR A BRAIN STORMER lol. 3:16 (yammie tony)
 
the head has been cut also but i have'nt checked the squish yet. the ports measure exactly what the bulletin suggest. i'll measure the carbs but does the timing not move with rpm ? thanks Andre
 
IF THEIR 77 SRX HEADS , THEY WILL HAVE 8F2 STAMPED ON THEM. AGAIN DON,T REMEBER ALOT OF CUTTING ROOM ON THOSE EITHER. YOUR SQUISH I BET IS PRETTY TIGHT. BE CAREFUL WHAT FUEL YA USE. I CAN REMEBER PRETTY TIGHT NUMBERS, BUT YA HAD TOO USE 110. MY GUESS THIS SLED HAS .44 mm CARBS. TIMING SHOULD BE SET !!!!!!!!!! 3:16 (yammie tony)
 
Well we're making proggress i just tried it on the grass and it goes out about 10 ft then yanks the skis and starts to haul . now i need to clutch it & get into carb jetting . Any suggestions for 500 ft on grass? thanks Andre
 
we changed the fly wheel,it had abad plug wire coming out of the coil so we changed it and we took the head off and found the seals out of place and squashed on the clutch side and letting a little antifreeze in the cylinder. so we changed the seals . Set the timing @ 2 mm. next i'll change the carbs and jet it proper but i need to find the specs for pilot ,main and air screw for carbs with no power jets and what ramps &sping in a 102 comet? i have the original yamaha clutch but it needs to be rebuilt. then gears ? mine has 18 -35

Andre
 
yammiegod the head ,cylinders have 8f2 on them ,the tunnel has 8f2 - 012490 and the timing cover has rx 433 -012490 . I'll check the squish today and get back to you .
THANKs Andre
 
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18/35 is good. With that comet I think the old 10,000 rpm set up that worked in many sleds might do it. Yellow Green comet spring, J weight noticed for 6500 ingagement and I think on the secondary we ran a polaris 42deg helix and a stiff spring wound to 18lbs. I'm not sure about this because it was 10 years ago on my wahl/rotax 440/crankshop opem mod sled. This set up was in the sled that took the High Points Championship on the East coast with PRO in 96. we also shimed the secondary so the belt would drop into the clutch to give it that snap shop off the line. Dean-o
 
LOOKS LIKE YOU HAVE THE RIGHT STUFF ANDRE, NOW LIKE DEAN SAYS, STAY WITH THE 18-35 GEARING. THEY SHOULD BE ALUMINUM GEARS AND LITE. RUN THE COMET, YELLOW - GREEN SPRING (# 208228A) HEARD THEIR HARD TOO FIND THOUGH. LIKE, DEAN I DON,T REMEBER WEIGHTS BECAUSE I USED SO MANY. P, N-1, K, J , C-1. WHATEVER WORKS, YOUR GONNA HAVE TOO RUN A 6000 TO 6500 ENGAGEMENT. THE WEIGHTS WILL NEED A NOTCH CUT. SECONDARY I USE STOCK YAMAHA SRX. USED STOCK 78 SRX SPRING WITH 340 SRX HELIX. YOUR GONNA HAVE TOO RUN AT 9800 TO 10,000. I HAVE A LL CARB SPEC,S, BUT YA STILL NOT SAY WHAT SIZE CARBS THESE ARE. ALSO I HAVE SET-UP FOR STOCK YAMAHA CLUTCH. GLAD YOUR BRING THIS SLED AROUND. 3:16 (yammie tony)
 
I checked the squish today and it measured .045 ,the carbs measure 41.93 mm line bored not taper bored. I have other carbs 40 &44 mm short and long stack,& original power jet carbs ! Gears are aluminum and he gave me a 19 tooth also .I haven't taken
the clutch apart but it has a light blue spring ,engages @6300 and peaks out @10,000 rpm ,just not real aggressive in the fist few feet ! maybe carb setting ? and -or ramp profile . Any carb & clutch specs Yammie god ?

thanks Andre
 
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