Author Topic: srx non starter  (Read 1497 times)

Steve Lake

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srx non starter
« on: March 02, 2009, 10:30:49 PM »
Well, just when you think there is nothing about a bike that you have owned/built/used for a decade that you can't fix.....John the plumber who i sold number 3 (srx6) to 2 years ago bought the bike round to mine this weekend with a non starting problem.
Since i sold it to him, he has had the engine rebuilt by Denver Motorcycles, with a pair of mikuni 34mm carbs and various other nice mods, and it has been an excellent bike, John adding over 20k trouble free miles since he bought it.
November 2008 saw the bike starting to have problems starting, though once running, was fine.
this got worse, until 3 weeks ago the thing just refused to start.
On saturday I removed and drained the tank, buying a gallon of fresh petrol, i checked the spark, and it was a bit weak, on testing the wiring the cable from the CDi unit to the coil was a touch intermittent so bypassed that, bypassed the side stand switch and the kill switch, with a new plug the spark seemed healthier, i checked and adjusted the valve clearances, and the exhaust valve lifter free play. Once this was all done, the engine still refused to fire, although there was an occasional bluddy great backfire!
So, thinking it seemed like spark timing I fitted a known working CDi unit.....still the same
and it was also the same with a different coil.
I checked the stator winding resistances and they are within tolerance...
As i had a spare good carb setup, i replaced those, still no signs of life...
That is where I am today....and now i must start to look elsewhere...
possibilities, as far as i can see are...
stator has moved or is damaged
cam timing chain has slipped
sticking valve (though compression seems fine)
rotor has slipped (unlikely, as it is keyed)
burnt valve
any other ideas will be most welcome.....

cheers

andy230

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Re: srx non starter
« Reply #1 on: March 02, 2009, 11:20:01 PM »
this'll be an interesting one steve!

bent valve?  tho noted about compression..
plug gap??  odd i know, but I once fitted a new plug to the skorp, only to find that the gap had been closed up to nearly nuthin!

a

Steve Lake

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Re: srx non starter
« Reply #2 on: March 03, 2009, 07:16:13 AM »
thanks for the input Andy
Yes, i had considered a bent or sticking valve (or burnt).. the plug gap is fine and tried several plugs
Next job (because it's easier than head removal :-) ) is a stator and rotor check.
cheers
steve

bullet350

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Re: srx non starter
« Reply #3 on: March 03, 2009, 09:01:38 PM »

 have you tried a known coil?

 if its gradually got worse then the cam timing must be okay, or it would have happened suddenly.
 
 also when you checked the spark, you presumably turned the motor over on the starter. did it have a plug in at the time? otherwise having no compression would give the electrics and easy time, and give you the good spark.

 one last thing, see if she goes with a bump start.

 bullet350

Steve Lake

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Re: srx non starter
« Reply #4 on: March 03, 2009, 10:37:09 PM »
Thanks for that bill...yes I have tried a replacement known good coil.
This is a kick start SRX....and yes, did kick it over with the plug in, and spark was good.

Pretty sure it will start on the rollers

Have now removed the stator,  stator and rotor look to be in good condition, and windings check out.

so next stage is to remove the head and check valves tappets etc i think.

crackedhead

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Re: srx non starter
« Reply #5 on: March 04, 2009, 12:47:04 PM »
I had a similar problem, which turned out to be a faulty HT lead. If you've changed the coil (and presumably the HT lead) that would rule that out though. I have a compression tester that you could borrow (mind you though, you could probably buy one up for the same amount as return postage would cost).

Good luck with fixing the problem.


bullet350

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Re: srx non starter
« Reply #6 on: March 04, 2009, 06:03:44 PM »

 another thought, have you bypassed the fuel tank and tap usinga new fuel pipe?

 i had a BSA B40 which had a fuel pipe that collapsed on the inside. pushing it onto the carb caused the inner to crumple up, but when removed was fine!

 bullet350

Steve Lake

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Re: srx non starter
« Reply #7 on: March 04, 2009, 10:42:14 PM »
thanks for the input guys...
Yup, the ht lead is part of the coil, and has been swopped out.....no change...
yes Bill, took the existing carbs off, and put on my trusty 40mm dellorto + manifold, fed from a plastic bottle on top.
.....no change

so tonight i have taken the rocker cover off, that looks ok on an initial inspection...tappets are in good nick and valve tops look ok.....next the head came off....and this too, at a quick glance is ok, though i will drop the valves ot and make sure the seats and guides are good.
This just leaves the barrel and piston, and i will say, the engine turns over SO freely, almost as if the rings wern't fitted...but the bore looks perfect.....will lift the barrel off tomorrow night..... then it's back to square one and re-check everything

themoudie

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Re: srx non starter
« Reply #8 on: March 05, 2009, 10:02:15 PM »
Aye SteveL,

Been on the road since Monday, so missed this scenario! :( Any luck? ???

This is me pondering after driving Totnes to Perth; so have you got a corroded connection or wire which breaks down under load. Sally had the earth wire from the coil which looked fine, but there was a crack in the insulation and the wire was covered in verdigre and near to breaking. Could this be a problem in one of the connection blocks with a bit of crap causing a short or not allowing the circuit to be 'made'? For it to be a gradual intermittent failure seems to be electricery rather than mechanical. The 'backfiring' would make me think spark timing, but again electrics!

Sorry, can't be more help.

My regards, Bill.

Steve Lake

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Re: srx non starter
« Reply #9 on: March 11, 2009, 12:28:11 PM »
OK...story so far....barrel off, bore looks good, but....with the piston at the half way point has a whopping great gap of over 50thou front or back....it is a short skirt wiseco 97mm...(50 thou is whopping isn't it?)
looks like piston 'rock' wear, also the oil rings seem to have lost their springyness, that is to say, barely protrude from the piston groove.

so....it's off for a rebore to 98mm, and new piston/rings/pin, clean the head up, reseat the valves, and start building it up again....

robG

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Re: srx non starter
« Reply #10 on: March 11, 2009, 08:56:42 PM »
Steve , Deja vu here old boy . Similar to the problems that have beset the Xs .3/4 will fire . 1/2 spark but won't run though spectacular backfiring from left hand silencer. Coils feed one pot on each side so not what I expected therefore not a coil. Petrol getting through , plugs are wet and black on 1/2.On top of this if the ignition switch is on or off the bike will fire .

I've stopped for the time being ,turning my attention to the running gear of the Rs .

Rob .

themoudie

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Re: srx non starter
« Reply #11 on: March 11, 2009, 08:56:54 PM »
Aye Steve,

Short skirt, same as was in Sally when bought, just not enough support or badly bored, honed and run in. That was a 634cc overbore!

Sorry to read of the expense. I hope you get it set up better this time.

All the best, Bill.

steveD

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Re: srx non starter
« Reply #12 on: March 11, 2009, 10:16:37 PM »
Yep I agree that's a bit worn. When I was Toolmaking I used to rebore my own barrels and the rule of thumb was 3 thou per inch of bore! ;D
If I'm not working I'll be away on my bike camping!

guest295

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Re: srx non starter
« Reply #13 on: March 12, 2009, 08:57:32 AM »
Short-skirt pistons always have short lives. For a bike that will be used on the road, the skirt should be about as deep as the bore size.

blew

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Re: srx non starter
« Reply #14 on: March 12, 2009, 09:44:52 AM »
Steve , Deja vu here old boy . Similar to the problems that have beset the Xs .3/4 will fire . 1/2 spark but won't run though spectacular backfiring from left hand silencer. Coils feed one pot on each side so not what I expected therefore not a coil. Petrol getting through , plugs are wet and black on 1/2.On top of this if the ignition switch is on or off the bike will fire .

I've stopped for the time being ,turning my attention to the running gear of the Rs .

Rob .
My GPz was plagued by intermittent misfiring,particularly at low revs.The misfiring plugs were black.Fitting D8's instead of D9's stopped the misfiring,although it was still rough at low revs.Finally tracked it down to incorrect float heights on two cylinders.Adjusting the floats restored correct firing......