Problems,problems.NEW head!

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voo2doo

voo2doo

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Hiya fellas
Just put my new Zenoah head on a CY crankcase.Standard CY bottom end and a Zenoah big bore head and for the first five heat cycles it was doing great.
When I took it out today (second time)it was going ok with a bit of tuning. Then when I returned to idle it cut out? When giving it a bit down the straight it was ballistic and then,when slowingdown it cut again.Heres the spec....
Zen bigbore head
CY 26cc bottom end
605 Walbro
standard air filter
Billet intake with teflon gaskets
FG tuned pipe
As i said it runs great when its at about 5000rpm but dies when i take it off throttle.I have tried richening and leaning the mix but it still has irratic idle.
Any ideas folks.
Cheers
J.
 
I do not know any thing about the 605 carb...May be jetted to small for the big bore kit
your using...I use 668,771.or 813 carb....I would say you have to make some adjustments for low side screw and Idle screw,,then the high side screw.....My suggestion is to get a 668 carb....Sounds like not enough fuel..and cuts out on you....Slawhammer
PS what's the plug color?
 
Last edited:
slawhammer said:
I do not know any thing about the 605 carb...May be jetted to small for the big bore kit
your using...I use 668,771.or 813 carb....I would say you have to make some adjustments for low side screw and Idle screw,,then the high side screw.....My suggestion is to get a 668 carb....Sounds like not enough fuel..and cuts out on you....Slawhammer
PS what's the plug color?
Click to expand...

Hiya slaw,forgot to say the primer bulb is virtually empty when its running.I haven't seen that on any other of my FG's.
My mistake its a 668 on it and I have a de-choked 605A lying about.Might it just be because its still new?
Got me baffled.
J.
 
Are the fuel lines new? what about the klunker in the fuel tank.?
Seeing how you have new engine now..I would replace the lines & klunker....
You sure the feed inlet line with the klunker is on the bottom of the carb?
Your return line about 1"inch to 1 1/2" in the tank....Your fuel cap is not plugged is it?..
your not getting fuel.....you may have pin holes in the line..or clogged klunker....
I replace my lines & klunker at least 3 times a year....cheap to do..always keep running
that way......Slawhammer.....
 
slawhammer said:
Are the fuel lines new? what about the klunker in the fuel tank.?
Seeing how you have new engine now..I would replace the lines & klunker....
You sure the feed inlet line with the klunker is on the bottom of the carb?
Your return line about 1"inch to 1 1/2" in the tank....Your fuel cap is not plugged is it?..
your not getting fuel.....you may have pin holes in the line..or clogged klunker....
I replace my lines & klunker at least 3 times a year....cheap to do..always keep running
that way......Slawhammer.....
Click to expand...

Yes Roger,the fuel inlet is new,its one from DDM, a translucent blue so i can see if there is any air leaks and not seen any yet.The clunk is still the original and i havn't really had a good inspection of it .I just put it one the end of the new fuel line.The fuel cap has been drilled to relive the pressure.
I'll check the clunk tomorrow and see if thats knackered.
Cheers again
j.
 
Ok I was busy up loading vid's..now have you checked the screen in the bottom of the carb for junk or crap there.....remove the carb..turn it up side down..un screw the 4
corner screws...lift off the plate..becareful of the diaphram...is the small brass screen
got anything there?....How was the carb running before the engine build?Has it been sitting long ? internal passage ways may have some blockage....Needle tips dirty...
Just a few more thoughts here.....Slawhammer
 
voodoo, I didn't see your answer for this one:

You sure the feed inlet line with the klunker is on the bottom of the carb?

I reversed mine and I was having the same problem. No fuel in the bulb and it wouldn't idle. It was because of reversed lines.
 
csp1971 said:
voodoo, I didn't see your answer for this one:

You sure the feed inlet line with the klunker is on the bottom of the carb?

I reversed mine and I was having the same problem. No fuel in the bulb and it wouldn't idle. It was because of reversed lines.
Click to expand...

Yes CSP ,the lines are on the right way round I've just got in my workshop and I'll let you know if theres any blockage in the clunk.
P.S,why does it say on your advatar 'Slawhammers intern' ? Just wondered.
Thanks
J.
 
voo2doo said:
Yes CSP ,the lines are on the right way round I've just got in my workshop and I'll let you know if theres any blockage in the clunk.
P.S,why does it say on your advatar 'Slawhammers intern' ? Just wondered.
Thanks
J.
Click to expand...

We both have Firehammer MT's and his thread from hell has helped me along the way! :P

Your problem just sounded a lot like mine a week or so ago. I had the lines reversed.
 
Hmmm,Jackobyte has just been down to my house(Over heating gears) in the MT thread and when he bought his they were the wrong way round too!
I've just took my carb off(668) and put a new choke on my 605A to see if thats the cause.I'll have to take it out later this evening or tomorrow to see if that has cured it.Just in the middle of trying to suss the over heating gear problems on my mates truck.The layshafts straight and everything is free?Well I'll put a new set of bearings in to see if thats the cause.
Cheers
J.
 
Goog to know you got it sorted out..I figured there was junk in the carb...from
all you said you did check and what was done.....Good for you my friend ..happy running
....slawhammer
 
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