TDC Gauge

70RT1 · 07-02-2012, 02:47 PM

I'm trying to set the timing on a 1970 yamaha 360 rt1. I'd like to get one of those gauges that screw into the spark plug hole, but I'm not sure if they work if they're screwed in at an angle to the piston. Any ideas?

ReconLdr · 07-02-2012, 03:41 PM

1) You could use a Dial indicator with a long plunger. Remove the spark plug(s) and turn the engine over by hand until the appropriate cylinder gets close to TDC. Install the Dial Indicator and continue turning until it reaches TDC. You'll know this when the reading on the indicator starts to get bigger. You may have to move it back and forth a bit to find the exact TDC, but it will work and also has many other uses.

2) You could use a wooden dowel (hell I've used a screw driver in a pinch). You just turn the engine over (BY HAND) and watch the dowel go up to TDC and down when you pass it. Again, you may have to work the crank back and forth a bit to find the TDC.

Note: I've never done this on a Motorcycle but have done it hundreds of times on cars/trucks. The concept is the same.

70RT1 · 07-02-2012, 06:09 PM

Thanks for the feedback. If I'm using a dowel or screw driver is it pretty accurate for trying to set the piston just after TDC? I think my manual's spec is something like 2.3mm after TDC. I've never done this before so there's a good chance I'm completely confused.

ReconLdr · 07-02-2012, 09:00 PM

Are you setting mechanical timing or ignition timing???

Mechanical Timing - keeps the piston from coming up and smacking the valves. This is really bad.... I can't say for sure that every motorcycle has them but every car has timing marks that you line up either with the other gears or an indicator cast into the engine or cylinder head.

Ignition timing - determines when the spark plug fires in relation to the piston in it's stroke.

When I replied earlier, I assumed you were just trying to find TDC. Not sure if using either method I mentioned earlier won't work if you need to find a specific position before or after TDC.

70RT1 · 07-03-2012, 12:28 PM

It'd be the ignition timing. What would you use to gauge that?

ReconLdr · 07-03-2012, 07:41 PM

Quote:

Originally Posted by 70RT1

It'd be the ignition timing. What would you use to gauge that?

I've never done it on a MC. I would assume you would use a timing light?!?! I hope someone with MC specific experience chimes in... I don't know what to tell you without looking at the book and/or bike.

07-02-2012, 02:47 PM	#1
70RT1 Newbie Join Date: Jun 2012 Posts: 6	TDC Gauge I'm trying to set the timing on a 1970 yamaha 360 rt1. I'd like to get one of those gauges that screw into the spark plug hole, but I'm not sure if they work if they're screwed in at an angle to the piston. Any ideas?

07-02-2012, 03:41 PM	#2
ReconLdr Master of Rex Kwon Do Join Date: Jul 2011 Location: Allentown Pa Posts: 830	1) You could use a Dial indicator with a long plunger. Remove the spark plug(s) and turn the engine over by hand until the appropriate cylinder gets close to TDC. Install the Dial Indicator and continue turning until it reaches TDC. You'll know this when the reading on the indicator starts to get bigger. You may have to move it back and forth a bit to find the exact TDC, but it will work and also has many other uses. 2) You could use a wooden dowel (hell I've used a screw driver in a pinch). You just turn the engine over (BY HAND) and watch the dowel go up to TDC and down when you pass it. Again, you may have to work the crank back and forth a bit to find the TDC. Note: I've never done this on a Motorcycle but have done it hundreds of times on cars/trucks. The concept is the same. __________________ "Political Correctness is tyranny with manners."

07-02-2012, 09:00 PM	#4
ReconLdr Master of Rex Kwon Do Join Date: Jul 2011 Location: Allentown Pa Posts: 830	Are you setting mechanical timing or ignition timing??? Mechanical Timing - keeps the piston from coming up and smacking the valves. This is really bad.... I can't say for sure that every motorcycle has them but every car has timing marks that you line up either with the other gears or an indicator cast into the engine or cylinder head. Ignition timing - determines when the spark plug fires in relation to the piston in it's stroke. When I replied earlier, I assumed you were just trying to find TDC. Not sure if using either method I mentioned earlier won't work if you need to find a specific position before or after TDC. __________________ "Political Correctness is tyranny with manners."

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07-02-2012, 06:09 PM	#3
70RT1 Newbie Join Date: Jun 2012 Posts: 6	Thanks for the feedback. If I'm using a dowel or screw driver is it pretty accurate for trying to set the piston just after TDC? I think my manual's spec is something like 2.3mm after TDC. I've never done this before so there's a good chance I'm completely confused.

07-03-2012, 12:28 PM	#5
70RT1 Newbie Join Date: Jun 2012 Posts: 6	It'd be the ignition timing. What would you use to gauge that?