Need help with timing once more...

[Coyote]

But I guess now that it is runnung on all 3 you're OK. Start the bike with the points cover off. You should see no big sparks. I don't recall you mentioning the 2.4mm you were trying to set it to before, and yes, there is a BIG difference between 2.4 and 3.37. What manual gave you that false information?? It is a GT550 right?? 2.4mm was for the GT380L only.

[Coyote]

OOPS! I guess I should READ. It is a GT380. Scrap everything I said I feel like a fool.
For what it's worth 380's timing changed some over the years.

[jbswear]

So...Which model is mine? It's a 1974.

[Craig380]

Brad, a '74 could be an L or an M. My 10c is to set the timing as per the M figures (2.3mm / 2.25mm), I promise you won't be able to detect any difference from the slight 0.1mm change ... better to err on the retarded side than advanced anyway.

[jbswear]

Brad, a '74 could be an L or an M. My 10c is to set the timing as per the M figures (2.3mm / 2.25mm), I promise you won't be able to detect any difference from the slight 0.1mm change ... better to err on the retarded side than advanced anyway.

Setting it to 2.4mm is what's causing my problems, I think. To set the left cylinder to 2.4mm means that the plate is moved so far that I can't set the right breaker plate so that it will even open up.

[tz375]

The points will ALWAYS open if the gap is correct, just not necessarily at the right time.

[jbswear]

The points will ALWAYS open if the gap is correct, just not necessarily at the right time.

Sorry. My mistake. I couldn't get the R breaker to close completely, so I was getting no spark at all. But now that I've reset it, I'm getting spark. I went back to the timing marks.

I want to check it with my dial indicator and see where it's opening now--closer to 2.4mm (as I thought it was supposed to be, but didn't work) or closer to 3.74mm as Coyote suggested. Hopefully I'll get to it tonight after school.

[tz375]

Get the gaps right first and see what the timing looks like. Then adjust the whole backing plate to see where that takes it to and fine tune the other pair with the points timing not their gap.

How EXACTLY did you get that 2.4mm on the dial to be different to the timing marks? There are two possibilities. A - It's one tooth out or B - the dial indicator is being read wrongly (easy to do). A dial gauge reads zero when it's at the BOTTOM of the stroke (good ones are about 90 degrees before zero to allow for overshoot). They are designed tomeasure the distance ABOVE a datum poin, so zero is the low point.

In our application, we are measuring negative distance i.e. below the datum. In other words, they read zero when the piston is low and read a higher number when the piston is at TDC. That means they cannot be read directly. You have to do some simple arithmetic.

What I do is to set the dial up so that it doesn't top out at TDC -say it reads 6.0mm. I zero the dial to exactly 6.00mm to keep things simple.

Then I rotate the motor backwards slowly to about 1mm mark on the dial (it will be 5mm down at that point) then I rotate the motor forwards until it reads 2.63mm At that reading the motor will actually be at 6.00-2.63=3.37BTDC.

If you has a $300 long travel dial indicator, you could zero it at BDC, and at TDC it would read 62mm and to get 3.37mm BTDC, it would read 62.00-3.37 or 58.63.

Hope that's clearer.

[jbswear]

My indicator won't read that far--it only has 1" of travel. I zero it at TDC, then rotate the engine so that it will read negative numbers.

If the bike should be set at 3.37mm, then that would explain the timing marks being so far out, right?

I have set it to the timing marks but haven't had a chance to fine tune it to 3.37mm BTDC. I think I need to replace the condensors, so until I can get a set of them I'm not gonna worry about it.

[tz375]

Not exactly. The timing marks are rarely spot on, but they should be close. I can't remember the whole tale of your motror, but is it possible that the timing wheel is one tooth out.

Q. How do you zero your DTI and read negative numbers? Mine will only zero at the start of travel. I have to "zero" it at some arbitrary number and carefully watch the needle rotate to be sure it would back the right amount, or I do the arithmetic. The gauge I use for timing is only a 1" - 25.4mm but that's enough for the task.

[Coyote]

Couple questions tz. Does the dial on your indicator not rotate? Can't you set zero anywhere you want? Talking in English (metrics aside), how can you check a 2.4" stroke with a 1" travel indicator??
I use a high quality Yuasa 1" travel indicator left over from my machinist days. Working through the plug hole I get about 600 thousandths travel. Plenty to get the job done. Find TDC - set zero - check where I'm at on the revolution dial and work from there.

[jbswear]

Not exactly. The timing marks are rarely spot on, but they should be close. I can't remember the whole tale of your motror, but is it possible that the timing wheel is one tooth out.

Q. How do you zero your DTI and read negative numbers? Mine will only zero at the start of travel. I have to "zero" it at some arbitrary number and carefully watch the needle rotate to be sure it would back the right amount, or I do the arithmetic. The gauge I use for timing is only a 1" - 25.4mm but that's enough for the task.

Mine is a digital indicator with an LCD display, not a dial.


I've pulled the clutch cover and tried to ensure that the indicator is set correctly, but it won't line up completely perfectly with the mark inside. When I line it up and then slip the clutch cover on, it shifts a tiny bit.

[tz375]

Chris, I have a number of different indicators, inch and metric plus a 75mm range that I use to check port timings etc.

For ignition timing I use a small one and yes, all of them can be zeroed. One thing I have found with people timing engines is that that they often try to read the numbers straight off the dial without realizing that it usually can't be read that way. You are presumably watching teh number of turns to get the right setting.

It's something that catches people out time after time if you'll pardon the pun. I was trying to determine what exactly was wrong in this case - if it was reading the indicator incorrectly or something else. In this case it seems that the digital indicator is being used, so that's not an issue.

Is there any chance that the pin which locates the timing disk and points cam is missing? I wish I could actually see what is being done here to determine what is wrong. It has to be something simple.

[Craig380]

I've pulled the clutch cover and tried to ensure that the indicator is set correctly, but it won't line up completely perfectly with the mark inside. When I line it up and then slip the clutch cover on, it shifts a tiny bit.

Suzuki ONLY intended those timing / indicator marks on that 3-leg rotor to be a rough assembly guide to the guys working on the production line, they are not accurate timing marks.

Manufacturing variances from machine to machine will mean the marks will NOT line up exactly on many bikes.

The marks will get you into the timing ballpark and the engine will probably run OK if you use them ... but it's unlikely to be accurate.

A while back I spent an evening with a dial gauge and my 380M. I found the factory 'timing marks' on my bike equated to 1.9mm BTDC. I also found my bike doesn't like the factory-specified timing for the 380M: I got pinking even when using 98 octane fuel. I now run it at around 2mm BTDC (the spec for the 380A & B) and it runs great. I scribed some lines on the 3-leg thing so I could easily check and set the timing as needed.

[jbswear]

I just ordered a set of new condensors from across the pond. When they get here I'll use my analog meter (I was using my digital) to set the timing. This weekend, though, I think I'll see where the piston is in relation to the timing marks now that everything lines up.

Even though I know I should wait, I can't help but go out and hear it run. Three prime kicks with the ignition off, turn it on, and it fires up on the first kick. I'm amazed.

But even still, if all of that is good, I have another gremlin to hunt down--the right cylinder's exhaust pipe is full of wet oil. Fun times ahead!