14cc head

crazy_mtb_2002

crazy_mtb_2002

New Member
#1
#1
On my old engine before I dropped a valve I put the 14cc head, with all the other typical upgrades, and I went thru pull cords and recoil springs like crazy, it would snap that thing right out of my hands all the time to the point I would give up if it wouldn't start easy, found my flywheel key way to be broken and assumed that's what caused it.
Decided to build up another champion, ran great, put another 14cc head on last night, and it's doing the same thing, tried 4 degrees timing, and 8, starting to run out of ideas here? Not high enough octane? Or am I just a whimp and the 10.0-1 compression is supposed to blow apart recoils, my arm, and make me walk away
 
crazy_mtb_2002

crazy_mtb_2002

New Member
#4
#4
It's got a 22mm mukuni carb, I'm working on tuning the jets right now, just tired of ripping my arm off like the good old days, stock cam, valve lash should be good, but I'll double check when I get home, Ngk plug, think it's 30 thou gap,
Just seems like it's detonating too early and that's when I feel it, thanks for the replies
 
Newoldstock

Newoldstock

New Member
#5
#5
Seems kind of odd.

More or les stock witha 14cc head should pull start fairly easy

Try a stock timing key.
Dish piston?

That should pull start like a dream at 10:1
 
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crazy_mtb_2002

crazy_mtb_2002

New Member
#6
#6
Tried stock timing, it's got a flat top, I must be doing something wrong the past 2 builds ;) I've always had issues with that mukuni, it's probably that :hammer:
 
minidragbike

minidragbike

Supporting Speed Nut!
#7
#7
Should pull start easy
Check your valve lash, make sure you have tight lash. If its to loose the compression release won't work.

Stop being a wimp :wink:
 
B

Bdmitsu

New Member
#9
#9
Is the carb and head all thats done to it?. Seems when someone mentions a issue.. you reveal that you changed something from stock. Please tell all and people will be able to help you more
 
crazy_mtb_2002

crazy_mtb_2002

New Member
#10
#10
Was the valves, they were out just a little, starts first pull everytime now, got the carb tuned in decently, just needs a little more messing around to be perfect, thanks alot guys
 
Newoldstock

Newoldstock

New Member
#11
#11
crazy_mtb_2002 said:
Was the valves, they were out just a little, starts first pull everytime now, got the carb tuned in decently, just needs a little more messing around to be perfect, thanks alot guys
Click to expand...
Just how much were your valves out?

This is just me but I set my valves by touch and sound.
I am to get as close to zero lash as I can.
Right now I am running about .001 itake and .002 exahust.
Thats measured after tha fact.

Since day one I think I have run tight lash based in part on advice from Guys like MDB and others and never had any trouble.
BUT that does not mean you can get complacent about it.
These engines genarly MAKE more lash as they warm up so its not a bad idea to check cold and hot as well as roll through and check the base circle ( intake only to be sure its not tightening up ). You can also see the compression release witht he lifter hits it and rolls off...

When the valve cover is off its also not a bad idea to check the head torque a couple of times to be sure everything has settled in and relaxed once the engine has heat cycled several times and broken in.
 
crazy_mtb_2002

crazy_mtb_2002

New Member
#12
#12
I'm gonna say about 5 thou, ice always done it by feel aswell trying to get next to none, it fired great once, so maybe it warmed up and loosened off just enough for me to have the re-occurring problem from before :) re-torqued the head studs, carbs pretty dialed in only then starving a bit in the top end, couple more jets and I should be properly ripping on this thing
 
Newoldstock

Newoldstock

New Member
#13
#13
Well there's an experiment for someone with time.

The factory spec is around .003 I think.
That leaves you out less than double the spec and I find it very hard to understand how that little amount of excess lash could creat you backfire and hard pulling.

Did anything else change?
Are these stock rockers?

Another thing I have honestly never thought to check or measure is the actual lift on the compression release.
OR any of the timing and durration on that.

Next I'd like to ask you more about the head piston and bump clearence you have on this engine.
You said 14cc and FT.
What is your in the hole?

And there seemed to be some confusion in your earlier post about compression ratio.
Did you do any significant work the head that may have reduced this to the 10:1 ish you quoted.

We have some baggage left here I just want to clear up.
I know I have been sloppier on valves than .005 and never had the troubles you discribe.
So I wonder if something else was going on at the same time you may have altered without realizing.
 
crazy_mtb_2002

crazy_mtb_2002

New Member
#14
#14
My first engine had ratio rockers, which ended up snapping and dropping a valve, it did the same as this engine starting wise, and never ran perfect

Picked up a new champion, slapped my old parts kicking around consisting of a billet rod flat top piston, aluminum flywheel, 22 mm mikuni carb, with fuel pump, aswell as studs all around, stock 14cc head with nothing else done to it but 18 lbs springs, what do you mean by in the hole?
 
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