NH Timming

[tobyshaw]

G'day everyone,I have just bought a 1949 NH 350.It starts and runs but it seems to be too far advanced.If I move the advance lever it revs its heart out.I would like to know the proceedure for timming it.I hope somebody out there can help.Best regards,toby

[nevhunter]

Toby, If the motor revs up a LOT when you advance it it is too retarded when you have not advanced it. Most engines are set by using a piston position . This is not as accurate as using a timing disc which requires the primary chaincase outer to be removed. TDC can be established by having the piston placed down an equal distance before and after TDC, marking those points and dividing them. This gives a much more accurate setting than just trying to find the top position by observing the piston stopping and starting. Set full retard at about 5 degrees before TDC and your full advance should allow about 38 degrees before TDC. You may not use the full advance position but it's there if needed. Idle will be normal when nearly full retarded and if you run it at full advance the engine will not like idling at that setting. This would be what I would call normal for a manually adjustable ignition situation. Nev

[tobyshaw]

Thanks for your reply Nev.Will look into getting a degree wheel.Best regards,toby

[john.nash]

A few posts down in this section is this:

http://forum.arielownersmcc.com/viewt ... ?f=8&t=671

Could I disagree with Nev on the timing wheel.
I realise that it's far more accurate (as is doing the timing with the head off and dial gauge on the piston) but the lever is there for you to fine tune.

Using a stick and a fag paper is near enough. I have the TDC tool and a mag ignition timing light, which might get me a gnat's todger closer but fiddling with the mag lever kinda negates that.
The timing light is actually more useful to save you from having to use one of your hands to keep reinserting the fag paper, when it falls out.

[bruce.carrad]

Someone told me once that they set the points to open at TDC with the mag on full retard. I have not tried that method myself but he assured me it worked for him.

[dave.owen]

Bruce it will work, and then use the advance lever to fine tune when running

dave

[john.nash]

I had the barrel off my VH and I can confirm that, with 1/2" advance, then full retard is TDC. I checked with a dial gauge.
To be fair, it's no easier to use TDC than full advance; both involve things down the plug hole, fag papers and mag sprockets

Anyone know where I can get one of those adjustable mag sprockets?

[tobyshaw]

Well I used a TDC tool and a cigarette paper,it shows 1/2" before top dead center on full advance and top dead center on full retard.However,when I run the bike and set the lever to full retard,it spits back through the carby every now and then.When I set the lever to where it runs without spitting back;It revs very hard.I have tried to set the carby but there is no response when I try to alter the mixture or the idle setting.May be the carby is already more than 1/4 open therefore out of the range of the mixture screw.Any ideas will be welcome.T

[nevhunter]

Your carby slide may not be going all the way to close or may be worn. A good carby will enable the slide to vitually completely cut off the air so slowing the engine will not be a problem if this is rectified. Nev

[john.nash]

Same as Nev.
Your bike SHOULD pick up revs when advanced and you adjust your carb speed down to where you want it (do it with the engine warm).

You should also be able to stop the bike by backing off the idle screw and make it virtually impossible to start (without opening the throttle)
If you cannot do that, then something is wrong. The slide may not be hitting bottom for example ?

A worn slide usually makes it impossible to get a steady idle, but it wouldn't usually keep the idle excessive unless it's in a very bad way.
Leaks between cylinder head and carb, also have the same effect.