SX200 engine problem.

[solostax]

SX 200 will not fire.

After finishing off a SX 200 engine rebuild (from the top end completed) fitted jetex 22mm ,electronic ignition,new cdi ,new plug/HT lead /plug cap ,new clutch ,etc etc.
Engine fired up and ran after just a few kickstarts. Stopped to re torque cylinder head /chaincasing nuts etc but will not start again other than one single big miss-fire.
Items checked :-
1/Timing re-strobed and has not moved .
2/carburettor bowl /jets /choke cable seating properly. Tried swapping with a known running carb (off my 175 engine).
3/CDI unit swapped out with a known good CDI /HT lead and cap.From my running 175.
4/Swapped spark plug as above.Tried various gaps all with healthy spark.
5/Tested ignition by leaving spark plug in and testing with another to confirm plug working under compression.
6/Confirmed fuel is reaching cylinder as direct injection with a syringe through the carb slide,resulting in nothing but a flooded plug.Tried purging fuel from carb ,plug dry.
7/With dry plug tried easystart through the throttle slide, nothing works.
I’m confident that the three essentials ,Compression ,fuel and ignition (with correct timing) are all present and correct, but am baffled that it started and ran .
I’ve been following similar threads on the forum and have checked, checked and rechecked all of the tips offered without success except the possibility of a damaged /twisted crank.To save wasting time by stripping the engine can someone explain how this could or might have happened?

[Raveydavey]

It has to be one of the three. Has a ring gone maybe? How are you testing compression? I use a compression tester which are quite cheap.

Also curious how you are testing timing if it's not running? What is the timing set to btw? Back fire is usually a sign of that being wrong

[coaster]

Your symptoms would fit with a sheared woodruff key, as above, you say that you "re-strobed "it but how could you have done that if the engine won't start

[solostax]

Thanks for getting back and the advice.
I really appreciate the spirit and invaluable experience of forum members and hope to contribute in some way to maintain this Godsend.....
Although there is no discernible difference in force needed to kick-start the engine, I will borrow a compression tester and get back with the result.
Would a sheared woodruff key alter the timing?
The firing point is set at 19°btdc and hasn't changed.
As for checking the timing, in my last thread I outlined an idea to turn the engine over by electric motor. Although the original concept was to keep it simple and cheap so it could be duplicated by others in similar circumstances, the finished set up involved using the two motors/wheels /12volt batteries off a disability wheelchair.
Whilst the device works It is not the simple and cheap solution I originally had in mind. However, knowing that it can be improved upon by the ingenuity of fellow forum members I will do a write-up with pictures.
Getting back to my present problem, I'm committed to thinking logically. That is, if it initially started and I have altered nothing what has changed?
On going over previous threads I read that a twisted crank could be the culprit. If so how could this happen? I'm aware that hydraulic lock can be caused by filling the cylinder with too much fuel but this was not the case.
Best regards

[Scooter Paul]

The symptoms described do lean heavily to a slipped timing. I have experienced similar before with a blown gasket causing a massive air leak. So despite fuel, spark and what appears to be good compression there is no ignition. Good luck.
Paul

[Warkton Tornado No.1]

I hesitate to say, but, with the World & his Wife being able to claim expertise in manufacture, the question you keep asking has an obvious answer.

IF the crank has twisted, it will have done so because it CAN!

What type is it & where did you acquire it, as that might help people on here to help you?

By now, you should have surely pulled of the flywheel to check the taper & key to ascertain if that is the likely cause as other people have advised.

It’s not worth speculating any further until you do that.

However, although I’m not wishing to start a debate about it, you can check the timing of an ignition without starting the engine by the careful use of an electric drill fitted with a 17 mm socket if you follow certain procedures. We have done so many times & it is very useful to be able to so, especially if you have neighbours within slapping distance.

I hope to have helped with this reply, not ruffle your feathers.

[solostax]

Scooter Paul and warkton tornado no1. Thanks for the responses
My electric motor set-up as described (photos to be uploaded)spins up the engine through the wheel/hub/gearbox.
On re-strobing the engine the timing had not changed,which leads me to believe that the woodruuff key is intact.
My plan of action is to put the engine/frame back up on the bench, set up the electric spin up motors ,and film the restrobe.
Because it makes sense that it is a timing issue I'm going to swap the stator and flywheel for the sake of keeping my sanity.
I will this time endeavour to video the results and upload to dropbox.
This engine was bought partially rebuilt,that is the crank,top end,mag housing hub etc completed. I was assured that all new bearings and seals were used up to this stage.I have changed the ignition from points to electronic ,installed new CDI regulator, sparkplug leads etc,shimmed the gearbox, fitted new clutch ,carburetor, using an AF exhaust and.whilst still installed in the rig frame it was hauled outside my workshop ,fuelled and after a few kicks burst into life.
Will take some time to work out the filming/uploading aspect of the operation but will be back asap.
Regards.

[Warkton Tornado No.1]

I look forward to that. Ultimately, I hope you can get sorted. If you're attempting readiness for the IOW, the filming can follow.

These electronic ignitions are substituted for points as a means of ensuring reliability. It makes me smile when people go to the nth degree to have their bike look as 'original as possible' (labels which would have been torn off asap, hidden hydraulics with a tell tale sign of a........hydraulic slave, disc brake windows, non ball end levers et cetera) yet certain changes occur as a 'given.' Each to their own. I just hope my very original Dell'Orto VHB 30 is not examined too closely to reveal it's internal modifications to enable PH type needles & atomisers to be used.

BTW. Spinning the engine up with an electric drill (NOT Impact Driver) doesn't have the additional load that your method entails. You can even tie-wrap the clutch fully in to reduce further! Just saying!

Good Luck!

[solostax]

Gentlemen
I humbly apologise for doubting for one minute despite specific advice my problem was timing.
On pulling the flywheel off, I discover the woodruuff key is sheared and the crankshaft shows some
evidence of scuffing.
What worries me is that this was a brand new item, which even when replaced may prove no more reliable.
My insistence that the timing was the same when re-strobed was due to minimal change observed
Whereas I would have expected a massive difference.
Sincere thanks to everyone who helped .

[Adam_Winstone]

Unfortunately, the woodruff key should play no role in stopping your flywheel from spinning, rather it is the matching taper of crank and flywheel boss, under applied pressure from the flywheel nut, that stops it from spinning. Your woodruff key has sheared because of one of the following:

1. Nut done up sufficiently tight.

2. Taper of crank and flywheel boss don't match. Whilst you should be able to fit new components without needing to lap the 2 surfaces together, the correct way to ensure that the tapers match is to use grinding paste to lap one to t'other (not ideal to do this in the motor as all parts must be cleaned perfectly with no traces of the paste left behind to fine their way into the oil seal!)

3. The flywheel boss is 'spreading' under load or cracking down the keyway, both of which result in the flywheel coming loose.

4. The crank, woodruff key or keyway in boss are incorrectly machined, resulting in the woodruff key sitting up too high. This allows the flywheel to tighten down on the woodruff key top, rather than the 2 tapers meeting and mating correctly. This has happened very recently when I went to strobe a pal's ignition timing. We had to wait for a decent replacement key to be posted out as neither of us had a spare. Once the new key was fitted the assembly sat correctly and this bike has since been to France and back without further issue.

You need to consider each of the above to see which might have caused the flywheel to come loose and allow the key to shear.

Good luck.

Adam

[solostax]

Thanks for the info Adam.
Whilst the engine is still in the frame/jig I will try another woodruff key.That is after I've checked for taper matching ,is
there a easy method of checking?
I torqued the flywheel nut according to the manual but noticed the nut didn't need the same force on undolng, is this a sign
Of mismatched tapers?
Regards

[Warkton Tornado No.1]

Hi.

A looser nut could well be due to unmatched tapers, but the key too high is more likely.

These days, they are soft, so can easily be modified. I've even made my own many times from washers or whatever, especially stepped keys for kart Motoplats.

As Adam said, they are only there as a positioner. However, you can speed up the lapping in process of the boss to crank with an (wait for it!) electric drill. You need something like an extractor in the flywheel nice & tight (via the bench vice) & the centre bolt of it locked into place (usually a common M12 x 1.75 nut) & spin it up.

Also, as it's confession time, I've had a key sit too high as well! That's how I had a fair suspicion of what your problem was.

You have rectification to do, but you must feel better knowing what it was!

[solostax]

warkton tornado no 1 and Adam
I am indebted to you for advice and solutions.As I have a few spares I first inked the taper shaft and in turn tried the original
and a spare flywheel to find which was the best surface to surface fit.
I have also fitted a used woodruff key and reset/checked/strobed the timing.
Tomorrow I shall take it outside and run it.
Whatever, I shall update with (good) news ......many thanks.
Regards

[solostax]

Warkton tornado no 1,coaster,scooter paul ,adam winstone. Gentlemen.

Put everything together and started on 4th kick.It would have taken me a long time to find the problem,so I salute
Your experience and help.
Many thanks.
Regards. Tryng to set a link to some pics
https://www.dropbox.com/sc/wiw5iacfho2t ... _HeUJDHnXa

[solostax]

Restrobe video
measures 20° btdc ,although 19° recommended what are the consequences of running around 20?https://www.dropbox.com/s/lfhnmac5kks9csd/20150826_155549.mp4?dl=0
Regards

[Warkton Tornado No.1]

The consequences are that it will worry you.

If everything is @ an optimum, that is, appropriate compression ratio, squish, jetting spot on, high fuel octane & you were intending to take it steady, you'd get away with it.

My bet is that you probably are unsure of the first three, & that is not a criticism.

After all, your set up is as standard GP, isn't it? It may even be the case that the oil you intend to use boosts the octane further.

Whipping off the flywheel is easier with an impact gun, but not that difficult without. It's taking off the tinware that is a pain.

[coaster]

Your symptoms would fit with a sheared woodruff key, as above, you say that you "re-strobed "it but how could you have done that if the engine won't start

Ahem....I think I mentioned a sheared woodruff key in reply number 3

Colin