08-13-2011, 08:54 AM #1
94 SLT 750, Help point me to the correct tech references.
This site has so much great info, makes it hard to find sometimes. Purchased a 94 SLT 750 with good compression that idled high.
-Took the carbs apart, cleaned and inspected all parts.
-Replaced fuel pump with pentagon HO pump and rebuilt it as well.
-Fuel line to each carb.
-Fresh gas and return restrictor still in place.
-Stock settings for high and lo speed ADJ screws.
Strapped it to th trailer, dunked it in the lake and tuned the low speed screws for max rpm, then opened them up an 1/8 turn.
Took it out for a run, checking the plugs on the water. Plugs had a brown tip and looked good to my very unexperenced eye. Puld hard and strong from idle or mid range. No hesitation at all.
Then it died. Restarted and had no power. Got back to shore and sure enough, I poped a hole in the center piston.
Pulled the engine to clean the bottom case and replace the center piston. Now the questions.
Can someone link me to the degree wheel and procedure for checking index?
Also the procedure for a leakdown test?
Can someone give me a rundown on the minimum I need to dissasemble to replace the center piston?
Thanks in advance. I have gone thru the service manual. I have all the torque specs and other info I need, Its just hard to find because you cant "search" the service manual.
This will be my first 2 cycle engine rebuilt. Thanks for your understanding. You have a great community here!
08-13-2011, 09:39 AM #2
- Join Date
- Oct 2006
- Cleveland OH
08-13-2011, 08:09 PM #3
Thank you for the quick reply!
I have now checked the index....within .5 degree
I have performed a leakdown test. Lost 3.5 inches in 10 minutes....within spec.
At this point im figuring that I need to check fuel pressure and check my carb settings as it must have been a tuning error on my part.
I have removed the center jug and piston. Jug seems to be damaged from th piston meltdown. Not only blew a hole in it but melted the edge of the piston. I have also pulled the bottom half of the case to clean up any metal particles.
-Can I clean and reseal the bottom sucessfuly without pulling the other two pistons?
-If so, do you lift th crank partially to lay the beed of sealer? Any help would be really appreciated.
-What, if any gaskets can be reused?
-The piston is stamped with "STD". I assume this is a non-overbore piston?
Goal- repair the engine with a used piston and jug for minimal cost, while still doing it "right".
If the answer was an easy find I missed, please let me know what search terms to be using.
BTW: anyone have a used piston/jug for sale?
08-18-2011, 09:08 AM #4
- Join Date
- Aug 2011
you have a major air leak, to cause that type of hole in piston. check reed valves also.
08-18-2011, 09:38 AM #5
It must have been a carb gasket problem (not able to check with a leakdown) or reed problem then. I have taken all the reeds apart and cleaned them so they lay much flatter (did NOT flip them). 2 were sticking way up in the center intake, but I was not sure if this was because of all the metal particles that came up and wedged them open or if they were open, and as a result allowed metal particles to come back up thru the intake.
08-18-2011, 10:36 AM #6
- Join Date
- Aug 2011
Where in Rochester do you live? we should meet up and help eachother out
08-18-2011, 12:10 PM #7
Near irond. mall right near the bay. Shoot me a PM sometime.
08-24-2011, 08:04 AM #8
Thanks to all the help, she is back up and running. 6310 RPM @ 47.6 mph. High speed turned out 5/8 more than factory settings. (Im running as rich as I could untill I noticed a performance decrease). I know this is not the correct procedure, but Im scared of burning down another piston.
Any further advice is welcome. From what I read, my rpm is about correct. Not sure if the speedo is accurate, but it feels like it does about 45 mph.
08-24-2011, 09:26 AM #9
It's probably slower than mine! :P
Is that what your MFD says for speed?
08-24-2011, 10:01 AM #10
Yes, MFD is 47.6 sometimes 47.9. Apparantly you did not pay attention as I was blabbering last night! I guess we will have to see who is faster....saturday...at 10 am. Just get you haircut another day. Going on the lake is way more important.
I believe yours is faster, but we need to bring a GPS.
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