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Post subject: Ignition timing
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NickIrons Powerband Master Location: Bienne Switzerland |
Having spent hundreds re-building my 350cc 4L1 motor,
I'm soon gonna have to tackle the ignition timing and
in order not to blow it up on the first day, I want to ask
how it's set up.
Before I removed the stator plate, I dot marked it and
marked a corresponding dot on the casing, so I can put
it back reasonably close to where it was. I've only ever
re-timed single cylinder 2 strokes with points, using a
strobe on the HT lead to match up the marks on the
flywheel and casing while it's running and adjust
accordingly. Whats the nuts and bolts of the LC timing?
Many thanks.
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Posted: Sat Jul 05, 2008 6:27 am
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Trig  One-handed Stoppie! Joined: 04 Aug 2003 Total posts: 2390 Location: On Cloud 9 |
Use a DTi or a degree wheel.
Nowt to say it was right before you took it apart.
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Posted: Sat Jul 05, 2008 9:07 am
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NickIronsPowerband Master Location: Bienne Switzerland |
| Trig wrote: |
Use a DTi or a degree wheel.
Nowt to say it was right before you took it apart. |
No, indeed, could have been all wrong, as I bought it
as a non runner, but for the 90 seconds it took to do,
I think it was worth doing the dot marks, so using a
dial test indicator to give me top dead centre,
which will also give me a good indication of how
twisted/or not my crank is by checking both sides
in comparison to the flywheel, what's the procedure
from there?
Many thanks.
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Posted: Sat Jul 05, 2008 10:11 am
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russ35031 Daily Burner Joined: 28 Oct 2007 Total posts: 129 Location: Northants UK |
Nick
Use a Dial test indicator to find TDC through the spark plug hole, then measure back 2mm BTDC by reading the gauge. You should then line up the `F` (I think its `F` if I rember rightly) on the flywheel to the mark on the stator pickup. Adjustment is by loosening the 3 screws/bolts on the stator plate (you should just be able to get a spanner in). Thats how I`ve always done it provided the bike is normal level of tune. I have heard opinion of going 1.8mm BTDC but never needed to.
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Posted: Sat Jul 05, 2008 12:51 pm
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NickIronsPowerband Master Location: Bienne Switzerland |
Many thanks Russ!!!
So turning the crank in the direction it will be running,
at 2MM before top dead, should be the point I'm aiming
at on a standard tune? If I understand you right?
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Posted: Sat Jul 05, 2008 2:47 pm
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russ35031Daily Burner Joined: 28 Oct 2007 Total posts: 129 Location: Northants UK |
Sure thing, rotate in the direction of running till you reach TDC on the gauge. Rock the flywheel back and forth a bit to make sure it is dead on TDC. Then set your gauge back to zero if you can or move the pointer to indicate zero, then move back 2mm on the dial. Pretty sure there is an arrow on the flywheel to indicate direction.
Only ever done with a dial gauge but pretty sure someone will come up with another method, but we are talking miniscule amounts and I cannot think of anything other than a dial gauge to do this.
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Posted: Sat Jul 05, 2008 5:04 pm
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NickIronsPowerband Master Location: Bienne Switzerland |
Great stuff Russ, I thought I'd got your first
explanation right, but always best to check.
Many thanks and ATB!!
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Posted: Sat Jul 05, 2008 5:27 pm
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cooler Suburban Commuter Joined: 17 Apr 2007 Total posts: 56 Location: leeds |
As said above, i did this just a couple of weeks ago but static timing always leaves me feeling a bit unsure, so, in my opinion, always double check with a xenon timing light at 2000 rpm and the " F " mark should line up a treat and if not adjust plate so it does ,,easy peasy japaneasy.
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Posted: Sat Jul 05, 2008 5:31 pm
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TrigOne-handed Stoppie! Joined: 04 Aug 2003 Total posts: 2390 Location: On Cloud 9 |
| NickIrons wrote: |
Many thanks Russ!!!
So turning the crank in the direction it will be running,
at 2MM before top dead, should be the point I'm aiming
at on a standard tune? If I understand you right? |
Turn the crank in the direction of rotation to find TDC, zero the DTi and then turn the engine BACK 2mm then line up the marks!
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Posted: Sat Jul 05, 2008 7:49 pm
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NickIronsPowerband Master Location: Bienne Switzerland |
Thanks for the hints and advice!!
ATB.
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Posted: Sun Jul 06, 2008 3:44 am
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mikejeff Mmm, Fully Synthetic! Joined: 11 Feb 2007 Total posts: 1117 Location: the glen of rothes. |
nick
if you get 2 dial gauges you can check for crank twist
a bit late if you've just rebuilt it tho but good for peace of mind
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Posted: Sun Jul 06, 2008 9:09 am
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| Lethal Got the Powerband! Joined: 26 Jun 2007 Total posts: 9 Location: Preston, Lancashire |
To get a more accurate TDC make a dead stop to to stop the piston through the plug hole. Set it so that it stops the rotation a good distance before and after TDC and mark the position exactly in between the marks and that should be exactly TDC without the rocking dead area on the dial gauge. To check the crank is not warped repeat ste process for the other cylinder and the TDCs should be exactly 180 degrees apart. 
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Posted: Sun Jul 06, 2008 8:47 pm
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