Will not start - intermittent spark

[beefos]

Hi, just joined the forum and had a good rummage through the topics.

Bought a Steamer about a year ago and love riding it. It has always been a difficult starter and just recently it got worse.  I changed plugs but no help. I check the spark and it seems intermittent - sometimes there is a spark and sometimes not.
I tried a new coil and exactly the same.
After reading the forum I have read about crank sensor failures. Is it under the cover on the right? If it is then I have measured the resistance at 500 Ohms - in the forum 0.6 ohms is mentioned. That is why I am questioning if I have the correct sensor! If it is it looks like I need to change it.  Thanks

[Red Lion]

As mentioned in my recent post about the crank position sensor, the failure in my case was a total and instant loss of all ignition. I did not experience intermittent ignition problems. You will also note that the Ohmic value of my defective CPS was as per specifications(6 Ω).

[beefos]

Oh yeah, I mean't 6 Ohms not 0.6!  Mine is 500 so must be dead! I've been quoted £44 +vat so will order on Monday.
Must have gone in a different way to yours due to the resistance and mine does intermittently give a spark.

[Red Lion]

Did you check the air gap at the TPC? 0.6-0.8mm. Maybe your gap is too big?

[beefos]

I checked the gap and it is 0.6mm.
I downloaded the service manual courtesy of Mustang - Thanks Mustang.
In that it says the resistance should be 530 Ohms not 6 ohm as stated earlier, so mine is about right.
Now i'm confused...

[beefos]

Got the sensor but looks like the dealer got in the wrong part!  Looks the same except the wires come out in the wrong place so wouldn't be able to fit the cover back on! If anyone knows the part numbers, they gave me T1290022. I'm guessing this is for a different model. Incidentally measured the new one's resistance and it is 580 Ohms.  Anyone know the size of the allen key needed for the bolts that hold the sensor in? It is between 2 sizes in my kit H4 and H5 could it be non metric?

[MarkShelley]

Bad starting is a symptom of bad valve adjustment, amongst other things of course, but I would get them checked out before you go replacing lots of parts.

[beefos]

Someone else mentioned valve clearance for bad starting - wouldn't have thought of that!

The dealer I got the crank sensor from tells me this part number replaces the original so is correct. Looks similar but the wire comes out in a different place...

Still not sure about the fixings though - looks like an Allen Key is required but is between H4 & H5 and looking closer seems to have holes at the corners, so is this a special tool required...?

[Mustang]

its not an allen key

IT's a TORX bit
can't recall the size , but they are all over the bike in different sizes , get yourself a good quality set

the one for the brake calipers is a T55 the one on the crank sensor you want to change is T10 maybe but I might be wrong
just buy a torx bit set  and use the one that fits

[beefos]

It is a TORX size T30. Was on really tight!
Changed the sensor but still doesn't want to start.

Turning over slowly (even with jump leads to a car battery).
Maybe it is the valve clearance then.

The sprag clutch may need doing as it is clunking a fair bit now with all the starter use...

[Mustang]

It is a TORX size T30. Was on really tight!
Changed the sensor but still doesn't want to start.

Turning over slowly (even with jump leads to a car battery).
Maybe it is the valve clearance then.

The sprag clutch may need doing as it is clunking a fair bit now with all the starter use...

go get a new battery before your sprag IS junk !

when was the last time bike ran ?

[beefos]

I think the battery is ok as it doesn't turn over any faster using jump leads on to a good car battery.
I did eventually get it started this afternoon and it runs good once it is running. But trying to start even when warm is difficult
as it seems to turn very slowly.  Would the valve clearance slow it down or is this a sign of the sprag not engaging correctly? It is getting very clunky now!!  It is a 97 model I'm not sure where to look for the cover if there is one, I'm assuming left hand side under the carbs? If there isn't one I hear it is a crankcase split...!

[rybes]

be careful jumpin ya bike off a car. i done it once on a bike n fried the alternator

[Mustang]

I think the battery is ok as it doesn't turn over any faster using jump leads on to a good car battery.
I did eventually get it started this afternoon and it runs good once it is running. But trying to start even when warm is difficult
as it seems to turn very slowly.  Would the valve clearance slow it down or is this a sign of the sprag not engaging correctly? It is getting very clunky now!!  It is a 97 model I'm not sure where to look for the cover if there is one, I'm assuming left hand side under the carbs? If there isn't one I hear it is a crankcase split...!

there isn't a cover on the sprag on a 97 .......early 94's were the last ones to have em .

seriously get a new  battery , if the bike doesn't spin good when hooked to the car
you have in this order from 1-3:

1. a bad connection with the jumpers either at the bike or at the car terminals

2. your battery is junk

3 . a bad starter motor

And from the sounds of things you have buggered the sprag from repeated attempts trying to start it with a weak / junk battery

[Bixxer Bob]

+1 (not that Mustang needs backup...)

My sister has a Triumph Legend. It cranked slowly both off the battery and with jump leads.  Despite repeated advice to buy a battery (iro 35 quid) she put it in to the dealer. He cured the problem by fitting  a new battery and releiving her of 100 quid for the trouble.