GT750 setting the timing

[MotoMartin]

Both the Haynes and Clymer manuals that I have for the GT750 show a dial indicator method and an "emergency" method of statically setting the timing to the actual marks. I don't have a dial indicator so I have statically set the timing to the marks, at the point where the points begin to open. My question is that neither manual mentions using a timing light, could n't I just set the timing with that?

[oldjapanesebikes]

Yes you can - if you are sure the marks are in the right place. For the most part, the timing marks are pretty accurate, but we (folks here in Calgary) have seen a few instances where that was not true. The dial gauge method is really the only way to be accurate and certain. I made my own tester for about $10 using a cheap dial gauge unit from Princess Auto and an old spark plug - I wrote about it here. If you are in the USA, then Harbour Freight would be a place to check for cheap dial gauges.

I'm sure other will chime in with additional comments

[MotoMartin]

Thanks for the info and link, I'll check it out.
Wow, I have not seen your site before, there is alot of good stuff there - cheers.

[Craig380]

It's useful to verify your timing marks using a gauge, then subsequent checks are much quicker (unless the crank twists, which is unlikely )

Also the factory timing setting is for an ideal, fresh, blueprint engine ... but as our bikes are older and looser, I found my triple felt "edgy" and gave a little detonation at the factory timing settings.

Retarding the timing by a little (from 2.25mm BTDC to 2mm) stopped the detonation and the bike runs and revs really sweet.

[MotoMartin]

With the timing light I can get the timing marks to align on the Center and Right cylinders but not the Left. Even with the timing plate rotated as far left as it will go, it still doesn't quite align with the mark.

[oldjapanesebikes]

With the timing light I can get the timing marks to align on the Center and Right cylinders but not the Left. Even with the timing plate rotated as far left as it will go, it still doesn't quite align with the mark.

Could be a crank problem - there are other guys on this board that are much more expert than I am who may comment, but the engine may have had a seizure, or hydraulicked at some point in its history putting that one cylinder out of alignment. Only way to know for certain would be to pull it apart.

I'd start with the dial gauge approach to see what you can figure out I think.

[Coyote]

I find this a little odd. I originally set up the timing on my 550 with an indicator. A long tedious process at best because you really should go 360 around to double chek your settings. Didn't actually seem to be in the same place twice. Always off .002 - .003.
The bike fired right up and I put 110 miles on it, but it just didn't feel right.. Time to retorque the head. While I was at it, I checked the timing with my timing light. Left was firing a degree or so late of the mark while the center and right were about that same amount ahead if the mark. I dialed all 3 in to the case timing mark. The bike ran lots better and is still set up that way today.

[MotoMartin]

Could be a crank problem - there are other guys on this board that are much more expert than I am who may comment, but the engine may have had a seizure, or hydraulicked at some point in its history putting that one cylinder out of alignment. Only way to know for certain would be to pull it apart.

The bike runs great at higher rpms, it pulls really hard at 5.5K, and revs freely, I briefly redlined it today. If it had a crank problem wouldn't it be more apparent, than just some mid-range stumbling?

[tz375]

The point Ian was making was that teh cranks are not pinned and it is possible that one or more cylinders are not correctly phased.

In addition the timing "wheel" has a fair amount of slop around the pin and can be bolted up out of the perfect position.

With points it is always a little bit of a crap shoot to know exactly the point at which they open. Open them slowly enough to see what's happening and the timing wanders a bit.

If you really want to know what is happening, use a dial gauge preferably without the head on. All DTI's will tend to skid slightly on teh outer cylinders and it's hard to be precise.

Bolt a timing wheel on the alternator and find TDC on one cylinder with a piston stop. Then set the timing on that cylinder and check where the timing mark is. repeat on cylinders 2 and three, but no not move the degree wheel or the pointer. Just check the piston position either side of TDC with the piston stop and read the degree wheel.

Set all three points to open at the same distance BTDC and not the positions of all three marks on the timing wheel. That is where it should be strobed at in the future.

The stock marks can vary slightly and cranks can be out of phase and tehre's only one way to know for usre - measure it very carefully.

[Craig380]

With the timing light I can get the timing marks to align on the Center and Right cylinders but not the Left. Even with the timing plate rotated as far left as it will go, it still doesn't quite align with the mark.

This can also be caused by the type of points you have fitted. The usual aftermarket Daichi-brand points have a shorter fibre "heel" than the ND-brand points, which can throw out your range of adjustment.

You can get around this by opening up the slot for the mounting screw on the point itself, using a rat-tail file. This lets you get the point gap right while still being able to set the timing accurately.

The other alternative is to make tiny adjustments with the point gap to dial the timing in. As long as the gap is in the range 0.3 - 0.4mm it's fine.

[tz375]

Good point Craig. I forget that some points are created more equal than others.

[oldjapanesebikes]

This can also be caused by the type of points you have fitted.

Excellent point (no pun intended ) Craig.

[H2RICK]

And you ALWAYS want to check your timing ~500 miles or so after installing new points. They WILL "bed in" somewhat as the rubbing block
gets "used to" the points cam. This also assumes that you have cleaned and lubed your points cam lubricating felt properly. It is amazing how many miles you can ride without messing with your points IF you lube the felt properly every spring. A quick check with the test light/ohmmeter is all you need in the spring when you have the felt lubricated properly and faithfully.

[MotoMartin]

This can also be caused by the type of points you have fitted. The usual aftermarket Daichi-brand points have a shorter fibre "heel" than the ND-brand points, which can throw out your range of adjustment.

You can get around this by opening up the slot for the mounting screw on the point itself, using a rat-tail file. This lets you get the point gap right while still being able to set the timing accurately.

The other alternative is to make tiny adjustments with the point gap to dial the timing in. As long as the gap is in the range 0.3 - 0.4mm it's fine.

Yes I have the Daichi points from Parts N'More. I'll try opening up the slot and see how it goes.

[Craig380]

Maybe try a tiny adjustment to the point gap before breaking out the files ... even a 1 thousandth of an inch change makes quite a difference to the timing setting. As said before, as long as the gap is still in the 0.3 - 0.4mm range then it will not affect running.