speedfight2 non-start

[andyjonc]

first of all an apology: i know it's likely that this topic has been discussed in the past. i HAVE tried to do a search, and read many threads already, but have been unable to solve my problem so am posting a new thread. please be gentle with me

i have a speedfight2. it used to run. then it sat in my shed for a couple of years. now i cannot get it started.

i currently have it connected to a good battery, i have checked spark (both seen spark on cylinder head and using a spark tester), i have fuel flow (with fresh fuel - checked carb, pulled hoses, observed fuel flow), i have removed exhaust in case it was blocked, when winding engine over using starter can see exhaust/unburnt fuel exiting exhaust port. i have checked compression and it has 60psi (i do not know the spec for this though so this may be too low?)

do all speedfight2's have an immobiliser? i didn't think mine did, but have read this as a possible fault on previous threads.
could it be the auto-choke? i don't know a lot about these

electrics on scooters aren't a strong point, but i would expect that if fuel is getting in, there's a spark, and a free exhaust... then the engine should run surely??

i am at a loss... can anyone help??

many thanks in advance!
Andy

[RhynoCZ]

I bet my money on the immobiliser.

A bypass unit: https://youtu.be/EcndPGpMKlA?t=1m33s ?
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Paulf]

60 psi compression is your problem should be twice that.
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Past bikes simsom mofa 1s, suzuki hustler 250 (£35 in 1973), suzuki ts125k, mz150, yamaha yb 100, honda pc50, honda vision 50, all 2 stroke - then cars - honda pcx 125 (sold) own honda fes 125 and Mrs 125 spares or repairs. Started 1972 all accidents walked away no insurAnce claims

[andyjonc]

ok so i reattached the exhaust just to double check the compression stayed the same. it stayed at 60psi.

i then noticed my compression tester was using a rubber extension hose... surely that would swell and affect the pressure reading?? so i removed that and connected directly to the metal connector. compression went up to 80psi. better but still too low.

so i put a little bit of oil in plug hole and refitted the spark plug. when i thumbed the starter it still didn't fire but did cough, once. encouragement!

i put my thumb over the exhaust and after a few spins the engine fired! it started!! i can only assume that blocking the exhaust momentarily, increased the pressure in the cylinder and helped the fuel ignite?

lot's of smoke but it's running. happy days!

[andys675]

the immobiliser won't stop them from starting, it stops them from revving up fast enough for the back wheel to move

however they do get spiked, and fire at the wrong point

sounds like compression is your problem, don't be tempted to fit a 70cc kit you'll open another can of worms with jetting/variator rollers
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Some people feel the rain, others just get wet.

[Paulf]

I am a little confused but your compression should be around 120 psi minimum. Putting oil in increasing the compression leads to rings. However you stated putting your finger over the exhaust raised the compression sufficiently to start. Large valve clearances are symptomatic of poor starting. You proved compression is a problem.
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Past bikes simsom mofa 1s, suzuki hustler 250 (£35 in 1973), suzuki ts125k, mz150, yamaha yb 100, honda pc50, honda vision 50, all 2 stroke - then cars - honda pcx 125 (sold) own honda fes 125 and Mrs 125 spares or repairs. Started 1972 all accidents walked away no insurAnce claims

[andyjonc]

[V2]

The valve clearances are simple on a two stroke - they don't have valves

[Paulf]

I apologise if your bike is a 2 stroke it can only be rings of worn bores. If its a 4 stroke, not to sure of a Peugeot speed flight 2, doing the valves is easy.
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Past bikes simsom mofa 1s, suzuki hustler 250 (£35 in 1973), suzuki ts125k, mz150, yamaha yb 100, honda pc50, honda vision 50, all 2 stroke - then cars - honda pcx 125 (sold) own honda fes 125 and Mrs 125 spares or repairs. Started 1972 all accidents walked away no insurAnce claims

[andyjonc]

Yes I was thrown by the valve comment I'll admit lol

Most likely piston rings then.

[Paulf]

You might be lucky and have stuck rings with the based on the time since it was last used.
____________________
Past bikes simsom mofa 1s, suzuki hustler 250 (£35 in 1973), suzuki ts125k, mz150, yamaha yb 100, honda pc50, honda vision 50, all 2 stroke - then cars - honda pcx 125 (sold) own honda fes 125 and Mrs 125 spares or repairs. Started 1972 all accidents walked away no insurAnce claims

[V2]

I had the same problem with an NS125R, while it sits the rings stick and hey presto you don't have enough compression to start the engine, Top end rebuild should sort it out.