shoot, detonation sucks

[ski4]

well i was doing some more tweaking and guess something was not right!

took a nice chunk out of the rear piston, not sure why, i am betting to lean inthe carb since that is what i tweaked with last nite, but damn she was running good

i think the bore can be used not even a scratch on it, i hope the same can be said to the crank

 

[Matt_E]

What jetting was this?

I might have an intact Pro-x 82.5. Not sure. I'll look.

 

[ski4]

i was running 75 pilot, 132.5 main, 1.5 ns and 65 gm spring

was having a lean spot in the low end so i decreased my pop off and put in a smaller pilot ( was 80 and 95 gm spring)

tuned in the carb and she ran like a raped ape for about an hour, then the dark cloud ( dj) rode it and blew it up in 5 minutes. ( just playing korn you did (i hope prevent further dammage by not starting it again)
i was thinking i was lean on top but i have a feeling it was more on the bottom

it was not starting as easy as it did with the 80 pilot i need to give it some throttle to get her to go

that would be cool if you do have another slug laying around but i am thinking you may not these were yours to begin with

i have a new set of 83 mm sudco's but would like to try and keep the bore

i think also gonna go up to a 77.5 pilot and 135 mains nexst time out

 

[Matt_E]

Oooooh....you're running the ones I was thinking of then. Sorry bud...

 

[ski4]

shoot, any one else???:frown: :banghead:

 

[MADMAT]

Bump. Any one gots an old 82.5?

 

[ski4]

well the crank is out , spent about and hour and a half with air oil and gas cleaning it out, there where a couple little tiny pieces of aluminum in it. seem a ok now though. stupid me, i forgot to take off the coupler when i pulled the motor apart. any ideas on how to do that with the crank out

 

[sflsurfrider]

the ring looks like its broken on the exhaust side. if it is, id inspected the exhaust port carefully and consider chamfering it.

as far as the removing the coupler, you can put the rear crack lobe in a vice and turn the coupler. i find that the head of a hammer fits well into the coupler and it gives you a handle to loosen with.

 

[ski4]

good call i will do that tonignt, thanks

 

[djkorn1]

bump...

 

[ski4]

well got the pistons yest, woo hoo.
the crank and bottom end is back together and ready to accept the top end, will deglaze tonight and slap in the pistons and pop on the head and pressure test

any thoughts on were i should go with the jettng?
when dj was riding he was not going wot. and it still deto'd

something happend when i lowered the popoff and decreased the pilot jet ( i am sure it had an effect on the wot fuel delivery and want to bump the main jet) but not sure if i should bump up the pilot too? man the bottom/ mid was crisp for the first time in a year and a half:cheer: :banghead:

it was a bit tough to start needed to goose the throttle to fire it up in the water with a load

 

[waxhead]

It looks to me that it broke of the side electrode on the plug
this is from deto

what size domes what squich clearance do you have
need to know more about the engine to make a diganostic about why it did what it detonatited

 

[ski4]

the electrode took a hit yes, we determined it got smashed by by debris from when the piston crumbled

the domes are for stock mm set up, i can't remember off the top of my head what they were in diameter
pistons are 82.5

not sure about the squish, paul actually machined these domes for me to get me up to about 180 compression ( and i sat at 178) cuz the cylinder had been decked too much i am 99% sure the squish should be ok though he had me get readings from the ports and what not to find out how to cut the domes. once i get the top end re assembled i will measure the clearance though

 

[ski4]

hey wax i just looked at the pictures i posted and the plug was not in the pic so i am thinking you thought the plug broke apart? the electrode just bent upwards and stayed intact, the chucks are pieces of ring and piston

 

[Jr.]

I have built & tuned many of these, the jetting is always
Pilot 75 L adj 1 1/4 T
main 135 H adj 1 1/2 T
stock spring & N/S

check to see your stator didn't move & is on the stock marks.
another problem I have been seeing is when the new ethnol based fuel is used. not only is there a water problem, but the octaine levels don't remain consistent. If you are running that fuel, raise your main jet one size.

On another note, did you happen to do a pressure check before tear down?
You might have had a small air leak & didn't know it.

ski ya, Paul

 

[ski4]

hey paul, i actually started with jetting by your rec at 137.5 and 75 and it was too rich on top and too lean on the bottom it seemed. ran terrible and was very hard to start in the water. at times i had to prime the motor to get it to catch

it was too lean on the bottom it seemed and upped the pilot to 80 . it made starting way easier and idled good but still had a strange low end hesitation.

the top end at 137.5 seemed off . it was gurgling and poping and would not rev out. so i went richer seqeuntly, took the jetting up to 145 ( which would not let me even get off idle, any gas there bogged it right out) so i worked back down and she seemed to like the 132.5 the best which bothered me a ton since stock with a b pipe should be 135


i monkeyed with jetting for weeks and finally got to where i was sitting the day it deto ( and it was the first time she seemed to realy ru n strong.) that day decreasing the pop and the pilot to 75 again


the stator was still in place and on the 0 mark, i didn't do a pressure test prior to tear down shoot

 

[Matt_E]

I think the 132.5 main is suspect - considering deto occurs (usually) in the high speed range.

 

[ski4]

I think the 132.5 main is suspect - considering deto occurs (usually) in the high speed range.

my fear as well. i think having the big pilot disuaded the motor from blowing up till i cut back to 75

on that note, there are a few dings in the dome as well that have been smoothed out by dj's brother, he says it should be ok to run .do you all concur?

 

[ski4]

the more i think about it i fear when i open the carbs i'll find i put in a 70 or a 65 pilot in the rear carb. i can see it now, all tired and wrenching and sticking in the wrong jet. man i will shoot myself.:lightning: :banghead: :woot:

 

[djkorn1]

Your top end was still not running right... As soon as that main jet would kick in, it sounded like it is starving to death for fuel. (Almost sounded like it was miss firing).

We will get it tuned in after a good dunking in MicMacs test tank. :arms: