Cannot get HT to fire up

[Irish John]

I'm trying to fix a near new 48cc HT which stopped firing before I tried to help the guy who owns it.
I've replaced the magneto & coil and the CDI.
I wired it up blue magneto to blue CDI & ditto for black then killswitch yellow stripe to black & then kill switch green to blue. That is all OK and I can see a spark from the plug but it might be a weak spark I don't know.
I've put a good NGK 6BHS plug in which is usually the best plug.
Cleaned the carby completely but still no firing up of engine.
Could it be the kill switch itself?
I adjusted the clutch so it bites really hard and should improve the spark.
I notice that the gasket on the inlet manifold is 10 times thinner than it used to be so not sure if air is getting in there. The thin gasket is just more quality fade since I last dirtied my hands on an HT 3 months ago. I've checked head bolts and exhaust bolts and inlet manifold bolts.
I don't think it is fuel problem but I'll replace the cock next.
Has anyone got any idea why this little beast wont fire up even on 400 metre hill. It fires but won't accellerate or stay firing if I pul the clutch in.

 

[BoltsMissing]

I wired it up blue magneto to blue CDi & ditto for black then killswitch yellow stripe to black & green to blue. That is all OK and I can see a spark from the plug but it might be a weak spark I don't know.

test it again with no switches connected, straight blue to blue, black to black.


Regarding carby and exhaust gaskets, make the same shape as port holes.

Seal up the carby inlet part where it slides into the manifold with level pink plumbers thread tape. I usually remove the clamp, wind some tape so it covers the slots in carby and then slide the clamp over the thread tape, and wind some on manifold. It Seals it good.

NGK plug, NGK Plug Cap and use a differant copper lead, the kit's copper lead is not the right type. The copper is too thin as compared to aussie made copper plug leads from auto electricians.

 

[machiasmort]

Did you get that thing runnin?

 

[247Jude]

I had a simular problem, it was the spark plug, the gap was briged by a small piece of metel. It looked like a small ball bearing.

 

[Irish John]

test it again with no switches connected, straight blue to blue, black to black.

Reply:
You mean disconnect the kill switch wires completely to diagnose if it's the kill switch. GOOD THINKING BOLTS WILL DO TOMORROW FIRST THING

Regarding carby and exhaust gaskets, make the same shape as port holes.

Reply:
I don't think this is necessary Bolts - too time consuming & almost certain its not the probleem. I could use gaket mastic compound stuff instead. Last option.

Seal up the carby inlet part where it slides into the manifold with level pink plumbers thread tape. I usually remove the clamp, wind some tape so it covers the slots in carby and then slide the clamp over the thread tape, and wind some on manifold. It Seals it good.

Reply:
That's been done at the outset but I could try yet another carby - would be third carby tried

NGK plug, NGK Plug Cap and use a differant copper lead, the kit's copper lead is not the right type. The copper is too thin as compared to aussie made copper plug leads from auto electricians.

Reply:
The plug & lead is part of the CDI I can't just pull it off and glue another one on to the CDI. This can't be the problem. I've had faulty CDIs before but not twice in succession that's too unlikely even by HT standards
This is the second CDI and lead/plug and it's a new replacement from ZBox as is the Magneto and coil. I put the magneto on carefully using a spacer between magnet and whatsit.

I think the first option might get me somewhere cos I haven't eliminated the kill switch yet and they are the cruddyest components in any HT kit. If it isn't the kill switch it has to be the fuel line or carby.
There is no firing up yet the plug sparks. Hoiw can that happen. It's a good plug - all my plugs are good & I have dozens of them.

WHAT ELSE CAN IT BE??? I reckon it must be the kill switch cos of all HT components my opinion of the kill switch is the lowest. Lower than whale excrement!!

 

[Irish John]

I had a simular problem, it was the spark plug, the gap was briged by a small piece of metel. It looked like a small ball bearing.

I'm using plugs that work on other HT motors mostly NGK 6BL Hs I think they are and they are usually the best. I have dozens of working plugs off other HTs. That ball bearing was probaly put in your plug gap by a disaffected worker who resented being herded into the factory at gunpoint every morning at 3AM. How else would it have got there seriously Jude?

 

[247Jude]

It was formed by the seating of the rings. It was runing fine and one time it stopped! I thought it was the cdi or magneto! But that little ball of metel was what I found! After changing the magneto.

 

[247Jude]

I use platium 4 plugs now.

 

[BoltsMissing]

Irish---Reply:
The plug & lead is part of the CDI I can't just pull it off and glue another one on to the CDI. This can't be the problem. I've had faulty CDIs before but not twice in succession that's too unlikely even by HT standards

There is a wood screw looking thing in the CDI where the lead fits, so you have to unscrew the lead. perhaps there is a bit of moisture, who knows.

Irish---You mean disconnect the kill switch wires completely to diagnose if it's the kill switch.

Yes. And if it works, no need to fix the kit's kill switch, the extensive length of wiring seem to tax a bit of it's potentially high performance. I use a On/Off toggle at the least as close as to the CDI as possible to keep the wiring as short as possible.
Had no switch once but it seems to make some purists react, so I now use a switch. But for testing and process of elimination purposes to find fault, no need for a switch for now.

Irish Reply:
I don't think this is necessary Bolts - too time consuming & almost certain its not the probleem. I could use gaket mastic compound stuff instead. Last option.

Ok, but I found the best approach is the, "leave no stones unturned" method, just in case.

Irish quoted: If it isn't the kill switch it has to be the fuel line or carby.

Remove the fuel tap and remove the kit's filter, add a in-line filter.

The kit's filter may have a tendency to restrict fuel flow.

Since reading somewhere once where a HT spark plug lost it's tip inside a new engine, then that get's thrown out to and replace with NGK B6HS, gap at .025 and ought to get the basics out the way.

 

[Irish John]

Thanks a lot Bolts - your perfectionism is worse than my own - you really have given me great advice covering every conceivable angle and I'll be onto it in the morning.
I'll bet you a schooner of 20:1 best 2-stroke mixture that it's the kill switch. I am seldom disappointed at my propensity for being wrong about these things so I look forward to losing. I've never found it this hard to get the HT to run.
A midi of best 2-stroke mixture says it's the Carby!