Scorch's GT380 revival

[Scorch]

Dial guage is here, tomorrow I will see about setting the timing. I understand that I need to have the points BEGIN to open at the designated BTDC position, right?

JBS said:

Basically, setting the timing is like such:

Set the gaps to .014" at wide open.

Find TDC on the left cylinder. Use a multimeter to set the left points to JUST open at the distance before TDC that the manual states for your years GT. For my '74, it's 2.4mm BTDC.

So I should use a multimeter? Let me ask one more dumb question: what do I set the multimeter on, voltage, right?
http://www.multimeterwarehouse.com/usingamultimeter.htm

and when the voltage drops, the points have begun to open? I assume the battery has to be in and the key on....

or am I checking for continuity ohms?

thanks!

[Buffalo-guy]

You can set the points timing without the power. Set the multimeter to 1X ohms, ground the black lead, and test the points openning with the red lead touching the electrical hookup. You are simply testing for continuity across the points, no voltage required. With that and your dial guage, you can't miss. Cheers.
Fred

[Scorch]

Naw-kay, still a bit fuzzy on the multimeter parts, but I was able to find TDC with the new dial guage.





And then reverse the crank direction to get the specified 2.30mm BTDC for the R & L, and 2.25 for C.



So, I was happy to see the small timing indicator showing L in the window.



Here I am checking the Center points, no buzz from the multimeter


And the Left points, the meter buzzes. I assume that's what I am looking for...



Points gap: .350 mm



Loosening a screw to shift the points and get them to open a bit wider




The results: http://www.youtube.com/watch?v=c3Ck8RJXcac

I was quick to open the oil pump lever, never did see any bubbles.
Pretty sure the center cylinder is not firing much if at all, the exhaust pipe never got really hot. I guess I will check each plug for spark, and then look into the carbs again.

Thanks for all the tips and feedback guys. I will check back in when I start digging into why it is not running well. I know, I am retarded as far as knowing where to apply the multimeter. Wish I could watch someone do this one time

[H2RICK]

Scorch, you will get easier-to-read-results and a faster response IF you buy an el cheapo analog ohmmeter from Circuit City/Radio Shack to check your points opening position. Digital meters are great.....for everything EXCEPT this kind of job. Their response time, IMO, is too slow. I have a Fluke 77 digimeter but I NEVER use it for checking points timing. I have an old analog ohmmeter and it gets used almost exclusively for timing chores.

[Craig380]

Scorch, you may be doing this already, in which case, ignore the rest of this post ....

After finding TDC, you should wind the crank backwards to about 4 - 5mm BTDC, then wind it IN THE NORMAL DIRECTION OF ROTATION (i.e. forwards) back UP to the factory firing point, and then check if the points are just opening.

This way, you're turning the motor the way it's meant to go, and taking up all the slack in the system.

As I say, ignore if you've already done this

[Scorch]

You're right, I did not think to do that. I will go through the process again today, I watched a couple YouTube videos and I think I have a better idea of the total process.

[Scorch]

@H2RICK

I'm not sure I understand what you mean by response time. My digital meter makes a buzzing sound when there is continuity, that's all I am going by.

I took the plugs out and looked for spark. The left cylinder was not making a spark, so I replace the points and condensor for that cylinder and after setting the points gap, now all three plugs are showing a spark.

I think I adjusted the points wrong yesterday. After reading up on this last night, I think I am supposed to rotate the crank and adjust the points gap when they are open to .035mm. The position of the piston is not important for this.

Then after setting all three points to be .035mm when they are wide open, I should set the timing of when the begin to open, starting with the left cylinder. I followed Craig's advise and made sure to run the crank the normal way an stop at 2.3 BTDC. And I think I see that the left points have to be adjusted by moving the whole plate. Then the Center and Right can be adjusted by moving just the points.

However, I have to admit that I do not get it, as far as using as mutilmeter to determine when the points open. When I put the probe on one side of the points and the other probe on the other side, it buzzes no matter if the points are open are closed.

I'm supposed to put a probe where the lead attaches, right? And the other on the case or a ground?




Does it matter if the ignition key is off or on? You know, I think I could do this, if I could get the continuity thing working.

[H2RICK]

My digital meter makes a buzzing sound when there is continuity, that's all I am going by.

Digimeters are STILL limited by their slow response time, even in the "buzzer" mode. Buy a $10 analog ohmmeter (or a suitable self-powered test light) to check your points-opening position.

The position of the piston is not important for this.

Well, kind of....You want the rubbing block of the point set you're setting to be on the highest part of the cam lobe. This is where you make your initial "rough" points gap setting for that point set. Timing comes afterwards.

it buzzes no matter if the points are open are closed.

You have a problem here. Either:
AA) the meter is not hooked up correctly or
BB) the point set has been installed incorrectly (grounded) or
CC) the condenser is shorted to ground

For AA) you have to be VERY careful with your probe to NOT touch the base plate (or any portion thereof) of the point set.
For BB) you may have an insulator washer on the wire attaching bolt of the point set in the wrong place.....or the little tubular insulator that fits around the bolt inside the points base plate is missing.
For CC) you need to disconnect the wire lead from the points first and then check the condenser from the lead to the condenser's casing with a suitable ohmmeter on the LOWEST setting. Make sure you touch the condenser lead wire to the casing to discharge the condenser BEFORE you attach your meter probes. If you get a low or zero resistance reading in this test, the condenser is shorted to ground internally and is history.

I'm supposed to put a probe where the lead attaches, right? And the other on the case or a ground?

Correct.....but this will ONLY work IF your points are installed correctly i.e. the wire and attaching bolt bits are installed properly. See above.

Does it matter if the ignition key is off or on?

Yes it does, IF you are using an ohmmeter (or buzzer), either analog or digital, or self powered test light. When using ANY ohmmeter on ANY circuit, that circuit MUST be non-powered (totally dead). Otherwise, POP goes the ohmmeter (or its fuse if it has one) and you let the "magic smoke" out of the meter. This, as we say in the biz, is a BAD THING.
Easiest way to be sure is to check the circuit with a voltmeter BEFORE starting to use your ohmmeter. That's why all properly designed meters have the voltage settings FIRST on the function selector knob BEFORE the ohmmeter settings.
So, after all this blather, the key must be OFF when checking points opening with an ohmmeter.

[Scorch]

Hi Rick, thanks a ton for confirming all this, you just boosted my "points knowledge" about 135%

I guess I will go get a test light tool, and give that a try. I see what you mean about the points shorting to ground, I saw that because of the felt washers and setup that the whole point is to allow transfer of a current through the points and when they open, it is interrupted. I will give this a really close up examination.

I checked the continuity with the ignition on, of course. I guess the multimeter survived, but I won't try it again.

Another question: with the ignition on, the points generate a smark spark when the open, is that the way it should work?

thanks! Hopefully this thread will help other inexperienced 2-stroke engine timers someday.

[Scorch]

ok, I think we have: BB) the point set has been installed incorrectly (grounded) or


I checked the meter against a new set of points not installed, and there was no cont. I will have to see why/how the points are installed incorrectly.

[Scorch]

After fiddling with it, the bike runs better and even idles. I took it around the block a couple times, very inspiring. Carbs need to be cleaned, but I have a bigger problem: the tach drive is not turning, and Gordon pointed out the same drive powers the oil pump.

[Coyote]

Hey Scorch (or anyone else following this thread), if your meter probes are 2mm, go to Radio Shack and pick up a packet of these alligator clips. I think there were 6 in a pack. These slide very snugly on the probes and make life a lot easier.

[H2RICK]

Excellent idea, Coyote. I have a set of alligators that I keep in the box with my ohmmeter. That way you don't need 4 hands to do the job....

Another question: with the ignition on, the points generate a small spark when they open, is that the way it should work?

If everything is correct you will get the odd small spark. However, if you have a bad condenser, you will get a spark pretty much EVERY TIME the points open WITH THE BIKE RUNNING. This sparking condition will ruin your points very quickly. The purpose of the condenser is to absorb the excess energy in the system so that the points DON'T spark.
The easiest test for a bad condenser, assuming you don't have a capacitance tester, is to visually observe the sparking frequency and intensity. Shut off the bike and then disconnect the suspect condenser from its associated point set. Make sure the points are connected back up correctly without the condenser and then start the bike back up. Observe the sparking action of the points again.
AA) More sparks without condenser?? = condenser condition is acceptable.
BB) Same sparks without condenser?? = condenser has failed and needs to be replaced.

I could go on for another page or so, but you get the idea....

[Scorch]

Ok, took some time out to update my GT380 page. I'm currently posting updates in the GT Triples yahoo group, here's a summary of where I stand.

Scorch's GT380 Revival

Long story is: I bought the bike 3 years ago. It ran fine until about 2 years ago, when it started leaking gas from one of the carbs. I pulled the carbs about three times and worked on the float height, replaced the needle valves and jets, until they stopped leaking. Tried to start it but discovered the nylon timing gear had broken So I pulled the clutch cover and replaced it. I was stymied about the timing and set the project aside.... that quickly turned into two years! Alas.

So, I've been working on it this month. Got it running, and been fixing various screwups by your truly. Now, I'm back to working on the carbs again.

[gt-keith]

Great photo's Scorch, things like these can be invaluble. Not only to remind yourself where all the bits go, but to the less mechanically minded who seem to be going round in circles, it all becomes very clear when faced with a simple picture.