IT 175 - Got spark when plug out / but cannot get it to fire

[Si1000]

Hi guys, I recently purchased a 83 IT 175 - the bike I grew up on. I am trying to get it running and have followed the usual, fuel, spark air etc, how ever i've run in to a weird problem and need advice from another set of eyes...
I remove the plug, and i've got a spark.
I put the plug bak in - and i cannot get it to even fire, let alone run. It's almost like it stop sparking once in place. ? I've removed the carburettor, the reeds etc and sprayed "start you bastard" straight into the transfers - but i still cannot get the bustard to fire, not even once.
I'm almost out of ideas and my leg is almost ready to break in two from kicking - any ideas - anyone ???
Cheers
Si.

[unitybiker]

if the ignition timings way out it will still spark.check n clean carb (especially if it;s been pre mixed)check reed in rightway round ,then check points gap .If it;s cdi ignitio then it may be the auto advance/retard but generally smaller 2 strokes dont bother with it .it's probably not sparking at the right time or somones had a go at he points and not set them on the flywheel marks.lastley clean the cylinder head plug thread and try a new/very clean plug .If its simple then i suspect the crap on the plug and thread is insulating the spark plug so it won't ' earth' the spark/coil.If it uses a disc valve system check it's aligned right.

[Handsome]

How many plugs have you tried ?...

Reason I ask is I had to once buy four to find one that worked in my old NSR, and they were new and set at the right gap, worked on the frame but wouldn't fire the bike at all...

Younger Brother had the same issue with an old scooter of his funnily enough...
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Previous Bikes...Honda NSR 125 RR...Kawasaki Zephyr 550...Suzuki SV 1000 S...Yamaha FZ8...Current Bike...Suzuki GSX-R 750...

[Si1000]

Ok guys - thanks for hints.
I've got 2 new plugs bought today. Both are sparking very well, ie I can open the gap to 1.5mm and still get a spark to jump. I even bought a iridium plug to see if that would help. Set plugs back to.8mm. So i think i can rule out, lead, coils etc as spark is solid and blue.

I pulled carb and re adjusted float level - but at this point it's not really a factor as I simply cannot get it too fire at all, let alone run.

I've pulled the reed / intake plate today and checked over everything - but again, this would effect running, rather than getting the bike to fire - wouldn't it ?

I'm really stumped - the timing marks are in alignment on the flywheel as well...

Question - When i had all of the intake apart, i sprayed some ether down the ports. Now i would of thought that id still get some sought of "fire" without any intake in place, - not to get it running - but to at least "fire" - anyone know if this is accurate ??
I then tired some fuel down the plug hole - and again, i couldn't get it to go close to firing - something is seriously wrong and it's likely to be somthin stupid...but i'm out of ideas ??

Cheers Si.

[smegballs]

Well I'd now look at comp.

If you have a spark and did the fuel down the hole trick then I would expect to have some sort of pop/fart/bang/hiss occuring.

A proper compression tester would be best, for now however the simple thumb test should suffice: Whip the plug out and get yours or someone elses thumb placed over the spark hole. Give it a good kick and it should blow the thumb off of the hole thus letting the air out.

No matter how hard you press, the engine should always blow it off

If you can hold you thumb down over the spark plug hole then theres something wrong and you don't have even minimal compression. No compression no bang...

[unitybiker]

you should be smelling petrol on the plug if not check the fuel supply is moving by draining the carb float bowl.also check theres no cut out killswitch attached,it may still spark intermittently with this shorted on ,but not enough to fire it.smell for the petrol

[Si1000]

The bike has good compression - I can't get my gauge in there, but it's enough to make kicking the bike over, a lot more difficult with plug in place. And yes, it will move my thumb quite easy. At a guess, i'd say it's about 80% compression of what i recall back in the day...

It does look like the plug might be getting a little damp when everything is in place, but i'm jumping the gun a little - i need to get it to at least fire - before refitting the intake.

I'm lost - do you think the plug might not be earthing out once screwd into the plug hole ? is there anyway to check this ??

Cheers again for all help - this really is a curly one.

Thnks Si.

[Handsome]

Two things to try off the top of my head...

Snip a little off the end of the ht lead if you have enough just to get to fresh wire and try that...

If that doesn't work try replacing the coil/lead as while it may fire when you've got the lead bent to reach the frame the wire inside may have a break in it, if you see what I mean...

I've also had those issues in the past and if I remember right I got the new coil with about two feet of lead from Busters Accessories, around a tenner I think it was...
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Previous Bikes...Honda NSR 125 RR...Kawasaki Zephyr 550...Suzuki SV 1000 S...Yamaha FZ8...Current Bike...Suzuki GSX-R 750...

[unitybiker]

AS NSR-AD says


a new lead or cap or both may help. But clearly smell for the petrol. An old trick from the days of briggs and stratton lawnmowers was to heat the plug in the oven and put it in hot to overcome any bad earth insulation problems with the plug. you should have a clear smell of petrol .

[Si1000]

This has been solved. For those that were interested - somehow a washr had become almost welded( ppl over tightening plugs) in top of plug hole, and it was absolutely covered, covered in crap - was not letting plug earth out.
Thanks for responses and efforts.

[27cows]

[Handsome]

At least you've found the cause...
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Previous Bikes...Honda NSR 125 RR...Kawasaki Zephyr 550...Suzuki SV 1000 S...Yamaha FZ8...Current Bike...Suzuki GSX-R 750...