I need a piston lesson (NEW ? VALVES!)11/14/12

[MRSOUND]

Ok Oscar.... Here's a pic of the valve seats. Hard to tell if there is a dual angle in there. Tried to feel it with my my finger nail but I cant really tell.

Shortline or anyone....Measuring the intake end of the carb I'm getting 18mm. If a stock 90 is 16mm what does it make this one? I had ordered a stock 90 rebuild kit. Will this have any effect on the carbs performance? (already rebuilt)If I remember correctly the main jet was a 65 that came with the kit.
Help out here guys. Learning as I go.

[shortline10]

The carb in your pic is def a atc90 stock carb so the kit should be Ok .

Ok Oscar.... Here's a pic of the valve seats. Hard to tell if there is a dual angle in there. Tried to feel it with my my finger nail but I cant really tell.

Shortline or anyone....Measuring the intake end of the carb I'm getting 18mm. If a stock 90 is 16mm what does it make this one? I had ordered a stock 90 rebuild kit. Will this have any effect on the carbs performance? (already rebuilt)If I remember correctly the main jet was a 65 that came with the kit.
Help out here guys. Learning as I go.

[MRSOUND]

Thanks Shortline! Next question is since this had the stock carb and stock exhaust with the oversized piston stuffed in there, can I assume thats why there was so much carbon deposits in the head and piston top? Lean condition? If it is any recommendations to even out the performance end? I have a cobra exhaust off a 110, will it mount up and help? Will changing the main jet be enough to get it the fuel it wants/needs? Open to suggestions.

[shortline10]

Could be a dozen reasons for the carbon build up. The carb is prob fine with stock jetting and the BB piston but if you put a HP pipe on it it will prob want a bigger carb or jets .

[MRSOUND]

Ok thanks again!

[MRSOUND]

Valves - Went to grind my valves in class and the valve grinder they have wouldn't chuck down far enough to tighten on the stem! Its a 3 jaw friction chuck similar to cordless power drills, just it bottoms out turning it in before the jaws contact my stems. Put them in a drill to see how straight they were and seemed like they were running out of round just below the valve head. Decided to just go ahead and order new valves(Shindy).

Questions:
1) Do i need to grind the new valves when they come in or should they be ready to install? (I will be resurfacing the head seat with a cutter)
2) If I do need to grind the new ones, how can I get it chucked up running true in the school grinder? I thought about getting metal shim stock to insert at the contact surface of each jaw. Any other suggestions?
3) What angle are the valves usually ground at?
Thanks
Mike

[shortline10]

Yes you defiantly have to seat the new valves with lapping compound . Just use a short piece of rubber hose that's tight enough to slip over the valve stem and chuck the other side up in a cordless drill . Man I shouldn't be giving up any of my old school secrets

[MRSOUND]

First off I want to say thank you again for all your advice & knowledge sharing through out this thread. I don't think I'll be taking any engine building business from you anytime soon. lol So will I still need to grind them (on the valve grinder) or just lap them?

[shortline10]

Depends if the seats have any pits or groves . Most times a little lapping compound and your done , after laping them look for a nice grey looking seat to show that their mating up well .
A good test is to hold the valve in place after your done and see if they leak by pouring a little fuel down the port .

First off I want to say thank you again for all your advice & knowledge sharing through out this thread. I don't think I'll be taking any engine building business from you anytime soon. lol So will I still need to grind them (on the valve grinder) or just lap them?