Couple of timing questions.

[gt-keith]

I think your onto something here Craig,
Suzuki did indeed change the timing quite dramatically over the years, and indeed did give quite a bit of tolerance when setting.
Interestingly they did not change the part number of the timing plate, so its safe to assume (dangerous I know) that the timing plate is the same for all models. Which model is it correct for?
Having said that, they did change the points cam drive gear (on the crankshaft end) some four times.
Footnote on the parts list says when changing cam drive gear on machines up to frame No 24759 which appears to be halfway through the 'K' model run, both drive and driven gear must be replace with the latest part numbers, thereby keeping the relationship between the crank, points cam and timing plate the same for all models even though the specified timing is different for some models.
Stick with the dial gauge !!

[jbswear]

@ JBS -- which specific model 380 do you have?

The factory timing spec changed from 3.0mm BTDC for the J model to 2.05mm BTDC for the A, although the actual allowed tolerance is HUGE ... the shop manual for the J gives the tolerance range as 2.52 - 3.76mm BTDC. That 1.24mm range of piston crown movement equates to a LOT of degrees of crank rotation ...

The VIN is GT380-63511. The date stamped on the neck is 6/74. I think that's a L model, right?

[tz375]

3.0mm is supposedly 24 degrees +/-3 degrees. I couldn't get exactly that answer but got very close.

24 degrees is about where one would expect that bike to be for the time and 21 degrees is probably closer to where it wants to be with modern gas which has less octane, and more chemical soup that the good stuff back in the day.

Bottom line is check it with a DTI or degree wheel and ignore the timing "wheel". Keep good records of where it was set and how it ran, so you develop a database of real results for your motor and what it wants.

Also try to be consistent with fuel if you are trying different things - try to avoid stirring in different fuel and confusing things. One variable at a time remember.

[jbswear]

Thanks.

I gotta say, you guys are great.

[two-stroke-brit]

on that note what octane fuel should we be using, as it appears to have an effect on the appropiate state of timming.
cheers mark

[Craig380]

We're lucky in the UK, the minimum octane at the pump is 95 RON. I seem to remember the Suzi manuals specifying 88 - 89 RON.

[jbswear]

Strange...I pulled the tranny cover off (tearing the gasket in the process) to check that all is lined up.

My indicator doesn't have that pin/key like what was posted earlier in the thread; instead, the indicator has a bent notch that lines it up--nothing to lose.

At 2.4mm BTDC, the indicator is to the right of the stationary mark.

If I set the points to open just as those marks line up, it's firing at 5.3mm BTDC.

Not only that, but when running at 2.4mm OR at 5.3mm BTDC, only the left cylinder is firing. Gotta figure out what's wrong with the carbs. Again.

[Coyote]

They ALL have a pin. You aren't looking in the right place. To get to it, you must remove the complete points plate (assembly), then the nut and the points cam. It's on the outside -- not the inside.
2 things are located by said pin. The timing indicator plate (part 20), and the points cam.



Remove the 3 screws that retain the points assembly. Pull the assembly and swing it off to the side. Remove the nut 18 and washers 17 &16. Then slide off points cam 2. Violla There's the pin. If some ham fisted PO lost that pin, you'll never get anywhere.
Pin 27 is still available from Suzuki. Part number 04221-03059.

[gt-keith]

Coyote you are correct, they ALL have the pin.
However, the pin locates/drives the timing plate and the small 'tab'on the timing plate locates the cam in relation to the timing plate, and the 10 mm nut keeps everything in place.
No pin and the whole timing could be anywhere.

[jbswear]

Okay...so how do I break that nut on the outside of the cam loose? I got the one on the backside of the nylon gear loose...

[jbswear]

Well...I know the bike WILL run on all three cylinders...Cranked it up and it runs on just the left. I pulled the filters off and had my buddy crack the throttle open while I sprayed carb cleaner into the throats. She started screaming, so I think another carb cleaning is in order...

[gt-keith]

I had the opposite happen, I couldn't get the nylon gear nut undone.
I used one of those cooks blowtorches with a fine pencil flame, gently heat the nut and it should loosen.
Worked a treat for me, along with all the crankcase/cylinder studs etc.

[Scorch]

Why did Suzuki alter the ignition timing over the years?
Did they alter the port timing in the barrels them selves? Or just change the ignition timing to suit the emission issues of the day?

gt-keith

Here's a photo of the 380's timing gears prior to assembly



Points timing plate should look like this.

Excellent! That answers a question I was going to ask before putting my clutch cover back on

[rbond]

If I may ask a stupid question? Have you had all three plugs sitting on the heads and cranked the starter to see if they all fire? My GT500 was a very hard starter especially cold when I first got it. Rebuilt carbs helped very little, turned out to be a restriction in the 'Y' fitting in the gas line. This tank has the wrong tap on it, it looks like the correct one, but has only one 'line out'. New fuel line and a 'T' fitting cured that problem instantly. Just a thought.......

[jbswear]

If I may ask a stupid question? Have you had all three plugs sitting on the heads and cranked the starter to see if they all fire? My GT500 was a very hard starter especially cold when I first got it. Rebuilt carbs helped very little, turned out to be a restriction in the 'Y' fitting in the gas line. This tank has the wrong tap on it, it looks like the correct one, but has only one 'line out'. New fuel line and a 'T' fitting cured that problem instantly. Just a thought.......

Kick start only.

While running, I've pulled the center and right plugs and they had fat, pretty sparks. Didn't pull the left because that was the only one firing.

Sprayed carb cleaner into the center and right carb throats and they started firing. Gonna pull the carbs and go through the jets and passages again. There's fuel in the bowls; I checked by loosening the screws a bit to see fuel flow.

My fuel line is a bastardized one...The tank isn't original, it's for a 550 or 750. I cut the mounting brackets off the frame and fabbed up longer ones that will fit. The petcock was shot to hell, so I just pulled it off and welded 1/4" sheet over it's mounting holes. Then drilled and tapped for a brass bung. I put an inline valve in, along with a filter. I don't have to worry about a bad diaphragm this way. Yes, it's ghetto, and yes, it's ugly, but it's only temporary until I figure out the eventual goal for this bike.

I plugged the vacuum line on the carbs to the tank so that they wouldn't run lean.