new ho 155z engine

[foxman]

hey there,got this new ho 155z engine from pitster pro and have had nothing but trouble with it running right,after mid range it doesnt run right,it sounds like a valve bouncing sound or rev limiter if ya get my drift,valve clearances are correct and carby is set right as well,was wondering if anyone has had cdi box issues with theres as i think that maybe the prob,cant be the carby coz i run my mates and his works fine on his engine which is the same!It doesnt rev right at all from mid range to full.any help would be grateful

 

[DHZ_XR8cing]

What are your valves set at?
What carbie are you using?

 

[foxman]

3 and 4 and am using the molket carb with 25 polit and 110 main jet,needle 2nd from the bottom,have been through all jet changes and it still runs the same,have also tryed a mikuni and didnt make any difference!

 

[MiniFighter]

Checked for air leaks around the manifold?

 

[foxman]

all good there mate

 

[DHZ_XR8cing]

when you say 3 and 4 what size is that exactly? Have you changed your spark plug? is your air cleaner clean?

 

[westy465]

.003 .004 thou

 

[DHZ_XR8cing]

I know what it is but some people get it confused. 3 and 4 is miles away from .003 and .004

 

[foxman]

changed plug to a new one and new air filter,.003 and .004 for valve clearance

 

[DHZ_XR8cing]

Have you checked your timing marks to make sure they are all lined up and your not a tooth out?
Im not familiar with the molk carbs and their jet sizes in relation to the OKO but on my bike with a 26mm oko im running a 40 pilot and a 102 main. Maybe your pilot is a bit small and your main a bit large??

 

[foxman]

timing is 9oclock to 12 oclock so thats perfect,my mate runs the same carb with the jet setting and his runs fine so dont think its the carb,got another cdi box coming,but might take a while to get it.Its been really disappointing as im pretty good with engines and have had previous bikes over the years and was dame set on this engine coz its a top engine,my mates engine hauls.Just hope the cdi is the key! mechanic from pitster pro has said hes found faulty cdi's now and then

 

[DHZ_XR8cing]

sounds strange. I have found that most things with these engines are simple to fix. Air leaks around the manifold is a very common mistake people make even after saying that checked it 3 times.

 

[sean01]

if ya mate has the same engine then he has the same cdi... swap it and see...

110 main... where did ya get that from? id never run a 110 main in a stock 155... way to big and would make it bog a lot...

and when you say after mid range, what part of the throttle are you referring to.. 1/2 throttle or 3/4 throttle..

your pilot should be fine as it will only control idle and off idle quality..

also remember gearing has a bit to do with it, if you got the gearing cranked right up with like 16/37 then the engine wont spin fast enough to use all that main jet...

might pay to change the coil too, just to rule that out...iv seen coils do some really weird things... stators too..

and to "DHZ_XR8cing" your pilot is miles too rich.... z155 with a 26mm oko should only have a 36 pilot

 

[DHZ_XR8cing]

36 pilot ran like a bag of ****. changed it to a 38.improved it but stil a flat spot off idle. put in the 40 and flat spot gone and very responsive

 

[sean01]

36 pilot ran like a bag of ****. changed it to a 38.improved it but stil a flat spot off idle. put in the 40 and flat spot gone and very responsive

seems strange that you have to do this... i have never come across a DHZ 26mm oko that requires this...

what other mods have you got??

 

[grnman]

he could have a carby float level that is way out.

 

[DHZ_XR8cing]

v2 head and s35 cam

 

[sean01]

he could have a carby float level that is way out.

very possible..

v2 head and s35 cam

those shouldnt change it that much..

 

[DHZ_XR8cing]

when I ran 36 or 38 and 100 I hade awsome take off from the line but ran out of legs.
When I changed it to 38 and 102 it had a flat spot off idle and lost a heap of pick up.
When I put the 40 and 102 it made it more ridable but im still far from happy with it.

 

[foxman]

float is fine,i was told to use a 110 for the molket from the mechanic from pitser pro,seemed strange to me too but i tried it and it did completely nothing.from half to 3/4 to full it doesnt rev right,the gearing shouldnt matter i think because it doesnt run right on the stand.my mate lives somewhere far away from me as we got together over the holidays,just rode my x4r instead once mucking around on the 155z ho,didnt think to change the cdi when he was here.Good point on changing the coil too