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Hi Guys,
Its been a while but ive finally ''almost'' finished my 'from scratch' MZ racer.
Its been quite journey and I have a track day at brands this Thursday which will HOPEFULLY mean I can reap the rewards of my labor!
HOWEVER... it just wont bl**dy well start!!
I have a very strong spark, timing is there (or there abouts! :o) but petrol no go bang in the cylinder :o(.
I have a PVL ignition from Burwins, wired it up correctly and timed it to the factory timing markers. The kill switch is in the correct position alowing a spark, fuel is getting to the plug... when I try and bump it (in 3rd Gear) it turns over maybe 2 or 3 revolutions then the rear wheel just locks up. It doent even try to start and im at a total loss as to what to try. I live on a hill and am certainly getting up enough speed to rotate the engine quick enough, there are no blockages in the intake or exhaust. It just feels like there's too much compresion?
Help me.... please :o)!
Ive got 2 evenings and a day to get it running. (nothing like leaving the most important bit till the last minute!! lol) |
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I was gona suggest that you maybe had the ignition wired up backwards, so it was firing after TDC, but sounds like you've got that sussed.
You havent got something jammed in there have you? bit of tissue, some rope from locking up the motor? You should be able to roll forever in gear with it not firing and the kill switch on (bet you someone did that this weekend :)
You should be able to start it in 1st. (i always used to, and with practice you should be able to get it to fire with about half a wheel rotation)
try starting it in 1st/2nd. But first figure out what's locking the motor up. |
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thanks for the quick reply pmb5,
Im 100% there is no obstuction or blockage. When I was spark testing last night (cable tie the plug to the head and push like a mad man) every thing turned over as it should in gear.
The issues begin when the plug is in and it 'trys' to turn over, you get... ahmm ''put put put.. bonk.'' (<- the written definition of sound :o)
It sends a real shudder through the bike and violently shakes the exhaust. But no gasses or anything. If it was at least sparking in the bore (even if the timing was off) i'd expect something.
:o( |
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sounds like a lack of crank speed top get the PVL going. i can't start mine on my own if it's not been started for a while, as i can't get up enough speed to bump it
like phil says, do it it first gear to get more crank speed, and get someone to push you.....so the back wheel doesn't lock .....they can just keep pushing you unitl it fires....
other thing to do, if you'd tried starting it loads, it might be a flooded, so is take the plug out, put in first gear and push around for a bit
also, disconnect the kill switch completely...it might be a duff
you coudl aslo try a road plug, just to start i for the first time, then put race plug back in |
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When I built my bike I couldn't start the bugger for love nor money until I figured out the kill switch was wired backwards from new but as you say you have a spark then it can't be that. Have you checked sufficient fuel is getting through to make it fire up and run? Even if the jet's blocked it can still allow enough through to make the plug look like it's getting fuel through but it's not enough to run. Another problem I had in my 125 days was the engine having a 'hydraulic lock' where the pressure would build up in the barrel, stopping it from turning over. I had to take the plug out, then replace it before the engine would turn over. Also, like Phil said in the previous post, try it in first or second gear, it'll probably be easier.
Giles #67 |
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Hey Giles Ive got one of your old front wheels on my MZ!! lol.. (from snett last year)
I thought about hydraulic lock, but as soon as i stop pushing or clutch in and start again it turns over.
I do wonder if fuel quantity is an issue, maybe i'll try a small amount of petrol rich pre-mix too. I know the carb is clean and blockage free, this s going to sound a bit silly but.... I removed the cable from the choke plunger, would that affect the carb petrol flow? I keep a little bit of throttle on when bumping to compensate for lack of choke but i know how some of these things seem to go in the weird world of carbs. I must say it has been distinctly lacking in petrolly smells that normally acompany a two stroke. But i hadnt thought much of it cos the plug smelt petrolly. Maybe this means im a donut and indeed she's not getting enough fuel to fire.
I'll try 1st/2nd gear tonight too, and even the road plug. I have an NGK B9 HIX (iridium?!) plug (well i have two but obviously am only using 1! lol). could that be an issue?
My mate is coming over tonight to give me a hand. He's big and manly so he can push my lardy ar*e up and down the hill all night!! ha ha
As a note on timing. Ive put the rotor on so that the key slot corresponds to the pin hole on the crank, and the stator factory timing marker is approx at 4o'Clock as per the instructions for clockwise crank rotation. anyone see any issues with this?
Really appreciate your help guys, hope to be on track with you all this year even if it is only one meeting ;oP |
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It should start even with the jetting WAY out.
I used to run my carb that way, no cable, but the plunger and spring etc still in there to seal it, so the choke was always off. It'd still start on a shut throttle, but once it fires you need to keep the throttle open to keep it running. I'd try starting it on a shut throttle.
Also, i have another query on the timing, i.e. i dont really get how you've set it. If you've got a PVL you can't use any of the standard stuff to line it all up, and you cant set it up without a dial gauge + adaptor. (or a pencil and some guestimating). If your timing is too advanced it'll be harder to start. MZ's are quite sensitive to timing (to get the performance) I did a lot of dyno testing which shoed you should set it between 1.5 and 1.7mm. 1.6 was the optimal. |
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you don't need a choke at all. block it off completely if you like - i have on mine
i doubt it's fuel quality.....it should fire a bit, even with shit fuel
what have you got the timing set at? general rule is about 1.65-1.70 BTDC
one thing i've done in the past that helped when it was being a bitch to start, was to chuck a cap full of fuel inot the carb bell mouth, so it sucked it through as it turned over....made it start every time when it was being tricky....you could try that |
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Phew.. thats ok then the choke is blocked off.
im approx timed for the BTDC as described however i dont have acess to a timing wheel/clock thingy to be 100% bang on (which I know is an issue) not to mention if the PVL set up info is in no way correct anyway then im probably WAY off with the timing. Oh the joys of an MZ... |
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The key slot in rotor and slot/hole on crank are not a guide.On the rotor there is a mark which denotes firing point,this should be lined up at TDC.When fixed on crank with mark at tdc turn engine backwards the required amount BFTDC.The mark on the stator should then be lined up with the rotor mark,normally around 10o`clock.If your stator mark is at 4 o`clock it sounds like you`ve got a stator off a go-kart,they are timed in reverse as their engines run backwards. |
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manxbob your a diamond mate. Now that you've said that it makes sense.
I'll try that tonight and see how I get on. |
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The timing mark on my stator is at around 3o'clock. It depends on how the thing is mounted on the motor. You need to get it right otherwise you could melt a piston very quickly. 1.6mm btdc is what gives best power. |
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okhay... im all out of ideas.
ive reset the stator (PVL 1427) and rotor so that all timing lines point at TDC. at very best i get a couple of revs (literally 2 or 3) and then nothing!
The engine certainly seems to go into some sort of lock, be it hydraulic or mechanical. it only does it when i try to bump it. It seems to coinside with the few atempts to fire i have had.
:o( |
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Not sure if its any help but these are the PVL part no's I use -
Stator PVL 458-1052 IDX
Rotor - Innenlaufer PVL 105 500-0952
Zundspule (Coil) PVL analog Typ 458 1 00
Steve Hill |
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If you take the plug cap off, and stick another plug in it and zip tie it to the head to form a circuit (if you dont have a plug in there and form a circuit you risk damaging the PVL) and just push it along, turning the engine over does it keep going? i.e. it doesnt lock up?
I'm convinced now your timing is so far out its stopping the engine. I take it you get some sort of bang?
If i'm right and your timing is that far out, you shouldnt try to run it anymore. Even if you get the timing close enough to run your going to end up causing some damage. Get a timing kit from Burwins, I think they only cost about £45 and include a dial gauge plug adaptor and screw in adaptors to length the dial gauge reach. Its a good bit of kit and you'll use it many times.
When a piston is £80 is it worth taking the risk?
If your PVL is made for the otherside of the motor, i.e. its from a motor going anti-clockwise you need to swap the plugs over on stator then get it marked up correctly in a timing jig. Brian Rogers has one and can do this for you. |
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