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Out of timing

Posted: Wed Apr 19, 2017 12:18 pm
by dan00001
Hi guys,

Firstly I'd like to thank you all for the excellent advice you give me whenever I ask a question, I know I'm not the most active member but your advice is hugely appreciated.

Anyway..

My sj413 is needing the timing set on a regular basis, about once every 4-6 weeks. I set the timing myself with a timing gun, I know your supposed to block of some of the vacuume hoses but I don't, and I get the rpm roughly right by setting the idle screw until it reads right on the tachometer, so not exactly perfect but there about!

Ill get her running sweet and then after a month or so I will start to notice a loss of power, especially at 3000rpm and above, and generally not running well, and the timing will be out!

She's had a new cam belt last year.

So what is wrong with her, or what am i doing wrong?

Thank you,
Dan.

Re: Out of timing

Posted: Wed Apr 19, 2017 12:26 pm
by ScottieJ
What carb are you running? are you sure thats just not adjusting itself.

Unless the dizzy is moving by itself then the timing should be staying the same. next time you time it up, put a mark on the dizzy adjustment to see if it's moving next time it feels like it has.

Re: Out of timing

Posted: Wed Apr 19, 2017 12:34 pm
by twiss
Out of timing.... so close but not quite

Image

Re: Out of timing

Posted: Wed Apr 19, 2017 12:35 pm
by dan00001
I'm running an su carb, setup by myself.

I will try marking the dizzy, but I tighten it down good.

When I check the timing, it has gone out, unless I am not doing a good job at setting the timing/or not being precise enough with setting the rpm?

Is there any other reasons why she doesn't like to be revved much past 3000rpm?

Another problem I sometimes get above 3000rpm is very little power under full throttle, but then if I back off to around 1/4 throttle, I get some power back (but not a lot)

Re: Out of timing

Posted: Wed Apr 19, 2017 12:37 pm
by dan00001
twiss wrote:Out of timing.... so close but not quite

Image
:lol: :lol:

Re: Out of timing

Posted: Wed Apr 19, 2017 12:39 pm
by twiss
You should definitely set the timing with the vacuum advance blocked off, drive it until it feels weird and then check the timing again with the vac advance off.
Also, is your vac advance correct. Should have NO suction on the hose at idle and FULL suction on the hose with revs.

Put the end on your lip and you will soon tell how much suction there is when it sucks your face into it :P

Re: Out of timing

Posted: Thu Apr 20, 2017 11:47 pm
by dan00001
Thanks swiss,

Checked the vacuume advance today, at idle, there IS suction which did not increase as I increased the rpm, and not at one point did it feel as if it would suck my face off :D

Re: Out of timing

Posted: Sat Apr 29, 2017 9:47 pm
by Rhinoman
Have you checked the crankshaft pulley woodruff key? constantly changing timing is a sign of a wrecked key caused by not tightening the pulley bolt adequately.

Re: Out of timing

Posted: Mon May 01, 2017 6:54 am
by twiss
dan00001 wrote:Thanks swiss,

Checked the vacuume advance today, at idle, there IS suction which did not increase as I increased the rpm, and not at one point did it feel as if it would suck my face off :D
If there is suction at idle then the carb is set up for a mini... you should block off the vac advance port and drill another one on the air filter side of the throttle disc, not the manifold side.
If you take the carb off you will probably see the tiny vacuum port just where the throttle closes on the manifold side