Thread: 785 Pro Motor Build
10-09-2010, 12:35 PM #1
785 Pro Motor Build
Here's the start of my winter project. It's a Protoype engine from back in the day.. a 97 I think.. It was built for the 98 season but was never ran.
So..This engine has larger exhaust vales,bigger tranfer ports and exhaust ports. Sounds like it will suck a lot of air. That means the right fuel delivery will be critical.
The crank has been knived also. pretty neat!
The rods have been smoothed and polished on the ends,, Probably used snowmobile rods and they needed shaving to fit. not sure on that exactly.
Engine is fogged and lubed with 2-stroke oil. turns great, nice n smooth.
I would hate to take the Pros motor out when its running so well. well almost--thats a different thread! The temptation to switch may be too great..
1 of the exhaust stem valves broke off a long time ago. Not sure If I can get the missing piece. I have the lower valve itself but it has been snapped off--like the engine fell over and snapped it off.
It can be fixed. So thats 1 hurdle already to deal with.. The rest of the engine is basically new.
stator,cdi,cases,flywheel,bendix,pistons,jugs,ete, ,are all new.
I have Frank Romeros Racing CDI for it also back in 97, its brand new, should work fine. It came with the motor. Lugs said its a older style cdi back in the day. early stuff.. Lugs is looking up the specs for me.
The engine was ran on a dyno for testing. should it should run now too.No info on that stuff.
Last year, I had some 785 parts(thats an understatement.lol) that I started to paint with the dupli-color red mettalic..
I'm going to do the whole motor like that. So I have the engine here in the pics with what I have done so far and what got done today.
I'll post more pics as I go thru the Painting progress. Any Machinist that could fix my valve,, Let me know please.
I was told as an idea to grind it flat, make that rod missing, tap both,insert double side threded pin,weld shut grind round again. that way it will never fall into the cylinder and grenade the engine.
I have a valve body extra here with the tiewrap,boot and spring on it, all I need is the rod with a nut on it and the hex made with the slits in it and the barrel for the cable to go into.
I'm not really looking to get above 150 PSI. I would like to run 93 still.. Maybe at some point, That could be changed. At that PSI, the motor will stay together. I hear 200 PSI likes to break stuff.lol
I would need a hardened stub shaft, driveshaft too if thats the case.$$$$ Can ya get driveshafts hardened? How much does that cost?
The motor looks goofy blue and that red doesnt it! lol I think I need some more paint.
Today I did the head bolts and the valves. The rest was done last winter.
I'll post a bunch of pics to check out if your bored.lol probably be in the hundreds by next spring. I know you all like pics!.
10-09-2010, 12:38 PM #2
10-09-2010, 12:41 PM #3
10-09-2010, 12:45 PM #4
10-09-2010, 04:14 PM #5
- Join Date
- Aug 2006
- Homer Glen Il.
i would get it running and put it in your pickup truck probrably more horse power then the original motor
10-15-2010, 05:02 PM #6
Update..One of my mechanics customers is a powersports guru on atv's motocycles,jetskis,snowmobiles and fabricates stuff for everything.. He said, if i have an original power valve to measure and look at , he can and will fix my broken power valve for me!!!!! Cha-ching! So next week, the power valves are going to his shop to fix the broken valve stem for me!
Thats soooooooooooooooo sweet!... Nothing else to fix on the motor.
10-15-2010, 05:22 PM #7
You need to add this to that motor, that will complete the ultimate race package!!!
10-15-2010, 06:10 PM #8
10-15-2010, 07:05 PM #9
Ok. Good Idea. Thanks Tony. And yeah, James, that will work out just fine! That should be good for rpm or 2.
10-15-2010, 07:26 PM #10
You should drop this in the pro and put the stocker in your slt
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