25.4cc 2stroke Zenoah "strato" starting problem (NEED HELP)

[GoldenEagleChris]

I have a race ported 25.4 Zenoah Strato Charged or commonly called "geo" engine on my GEBE rack mount motor bike.

I have torn her down and rebuilt her so I know my way around this engine.

I am pretty good at troubleshooting but alas, I must turn to my fellow bikers for possible help.


Here is the problem.


I only get to start and ride my bike on the weekends.

I notice this problem only when the engine is completly cold and has not been started.

I will first say that I am running a Walboro WA-167 hipo carb and it has never given me quite this much trouble.

The settings are at the low end 1 1/8 turns out and the high is 1 1/4

These have been my standard settings and I usually do not deviate from this.


I cannot get this thing to start on one pull any more, in fact sometimes I sit there for like 10 min flooding the darn engine I pull so much.


Yes I reset the settings on the carb and try again...

Then I will pull the spark plug, blow off the gas, and start over, open the gas cap, let it breathe, ect.

15-20 min later after I let it sit and drain, I will come back to it and there is a 50/50 chance it will fire up on 1-2 pulls and then after it is warmed up it will start on the 1st pull every time and I am happy.....until next weekend...

Start process over again....

At this point, I dread having to start my engine cold.


I have torn down the carb, pulled her apart and she seems fine.

I crank down all the screws on the intake manifold/ carb screws and sometimes they have some turn in them, sometimes there as tight as a virgin...

I just dont know why my engine has ssoooooo much trouble starting cold...

If I ever try to sell it, it would be a hard sell for someone, but they would shure get a laugh watching me yanks on that pull start like a retard...


I have even considered going back to boring old stock and praying it would fix it.

'At this point I would sacrifice some mph's if it would just start on 1 pull cold.



Any suggesstions as to WTF is going on?

 

[Old Bob]

Who did the porting? (too much intake duration will make for hard starting)
Did this problem start right after the porting was done?
Have you put in a new spark plug?
Check magneto gap?

 

[GoldenEagleChris]

Daves Motors did do the porting. However when I recieved the cylinder I compared the port job to the old one I had and it seemed a bit on the weak side. So I asked Daves to report a little more hard core, but that was well over a year ago and I never really had a problem with it.

I checked the spark and it seemed strong, but I guess I could put a new plug in, New or not, it wont work if the cylinder is flooded and the plug is doused with gas.....

I did think for a second that it was the magneto, I was taught an old trick by a goped racer I will share, the magneto is able to be perfectly spaced from the flywheel with a simple business card. That give it a close gap without hitting the flywheel. I have never had a problem with this either.

I just dont know.....Mabey I need to put a new cylinder on it and hold the porting?

Really? Could it be the whole da rn cylinder giving me this problem?



But when the engine is warm it runs like a dream......


Perhaps I need a more ignitave fuel / oil/ methonal mixture to make it ignite.


One last thing I noticed as I was figiting with it yesterday. It seems to like a lil rich mixture of fuel approx 1 full turn when it is cold. Seemed like after it started I could back it off.



Oh yea I forgot to add in my original post that when I get to the bike after it sat for over a week cold.

Some cases I will pull once, it will fire up then run for 5 sec as if it burnt up some unused fuel in the engine then it dies and it is pull, tug, and curse until it starts and then I am good to go......

Any more suggestions?

 

[JemmaUK]

I have a couple of suggestions

I used to have a standard ported Zenoah but didnt have a single problem.. I have since moved onto a 32cc GE kit and use a special mixture with it.

Get hold of some 12% nitromethane fuel and add about 50mls of that to a gallon (4.54 litres) petroil at the usual mix. This will help with starting. The 32cc Tanaka engine was a pig to start cold - needing between 5-10 pulls to get it going - I always had the bike in the house when it was really cold so I suspect it would have taken more... with the nitromethane fuel it fires first pull and is a little more responsive as well.

It might be that using the nitromethane will help with your problem because it burns at a lower temperature than does the normal petroil mix (sort of like using ether to help start a diesel engine). Its enough to kick the engine over and raise the compression chamber temperature to burn normal fuel.

If you have ported the engine and have not adjusted the carburettor it is very likely that the mixtures will be off - this will make for very hard starting on any engine... in which case if you can adjust the carb you should do so...

have you also tried starting the engine for the first time cold (ie at the start of the weekend) without choke to see if that makes any difference? also slow pulling the motor before you try and start it might help (so it turns over compression a couple of times) - priming the engine.

It might also be an idea to get the bike started once in the middle of the week and allow it to warm up and then shut it down ... which would make for easier starting later on.

The fact it only does it when the engine has been stood for a while is the part that doesnt make any sense for me - it shouldnt make any difference unless there is some sort of issue that is causing an occasional problem like a fuel pressure issue...?

 

[Old Bob]

If the carb diaphragms are more than a year old, replace them and try it.
Also replace cylinder base gasket.
If that doesn't help:
Put a new ring in it and try it, Zenoah had a batch of rings that were soft and would lose seal, making for hard starting etc.