Not Really a Bob, Not Cafe, GS300 Suzuki

Mike Lawless

2006 HD Softail Deluxe - 2014 Triumph Bonneville
Checked the battery voltage. It was 12.6. I did not check it running, but that voltage would indicate that the charging system is functioning for as long as it's been running since I last put a charger on it.
Popped the carbs off, and they were clean as clean can be inside. Regardless, I'm gonna soak 'em and blow 'em out real good. I think while I'm at it, I might as well go up a size on the pilot jet which is 17.5 now, and go up a size on the main. It's 115. I figured since I opened up the exhaust and put pod filters on, it's probably a tad lean. The slides and slide bores were clean with no scratches, and the diaphragms were good. This I was very glad of, because the prices I've seen on replacement diaphragms is more than aftermarket carbs would be!
Although, pulling the plugs, the base was a bit sooty, but the porcelain was white. I was trying to get home, so I had the choke half way out.
Just for giggles, I did a compression test. 180psi on both holes stone cold.

Now, I've read here that it's common practice to "put a washer" under the rods. I know this is to lift the metering rods out and I know they are tapered. Much like a Rochester Quadrajet automotive carb.
Is there a "washer" available that come in certain thicknesses? Or is a "seat of the pants" thing and one changes it, see how it goes, then adjusts from there?

Anyway, after this, we'll see how it runs. I reckon it would be down to the ignition system if it still misbehaves. However, I've been around long enough to know what lean feels like. I even know what "super lean" feels like and have melted plugs and torched cylinder heads to go along with that feeling. (V8 and VW race motors)

And this thing feels lean.

The good thing....
This uses the same spark plugs as my VW racer. I have plenty in stock! Even unmelted ones.
 

Scruffy

West Tennessee
Does it have vacuum operated fuel valves? Is so that is another well known issue. And not just with Suzuki, vacuum operated petcocks are about as useful as tits on a frog. If you have vacuum petcocks, and the bike acts that way again, switch them from on to prime, as prime completely bypasses the vacuum circuit in favor of a mechanical direct flow circuit.

Take a picture of the petcocks on your tank, one of the side view, one of the mounting system. Odds are somebody on here knows a work around if they are vacuum units. If they are mechanical, you can get the same symptoms when the selector plate gasket gets worn out.
 

Mike Lawless

2006 HD Softail Deluxe - 2014 Triumph Bonneville
Thanks Scruffy. It does indeed have a vacuum petcock and after seeing how clean the carbs were inside, I am starting to suspect that may be the prime culprit. My plan is to do as you suggest and run it on prime until I can get a simple "On/Off" unit. It takes about a week and a half to get stuff from DCC, so I'll probably get that on order along with a few assorted main jets and a few pilot jets too. Hopefully, I can get this thing back together so I can ride it for a while. I'd hate to do the winter tear-down with it running poorly and not getting that resolved first.

The stock petcock bolts to the bottom of the tank with two screws. Seems like a simple matter to either hack off the flange and tap the flange for 1/4"NPT threads, or make a new flange altogether. Fabbing stuff like that is a piece of cake.

The thing that concerns me the most is the possibility of a misbehaving ignition module. It doesn't look like a stock module is available, and a cursory search hasn't turned up an aftermarket bolt in replacement. I might have to adapt something if the trouble ends up being the electronic ignition. I hope not!
 

Scruffy

West Tennessee
So a Savage petcock. Which is always replaced by a Yamaha Raptor petcock. We use the 660 petcock on our 652s, your 300 should take a smaller Raptor unit. Ought to cost you around $20 out the door at any Yamaha dealer.
 

Mike Lawless

2006 HD Softail Deluxe - 2014 Triumph Bonneville
Well dammit. Somehow, I seemed to have "screwed the pooch".
I got the carbs back together, but I can't get the right side to stop leaking. It fills up the bowl, then leaks out of an orifice at the carb opening. I presume that to be the bowl vent.
I've had it off and apart a half dozen times, and I've even swapped sides of the needle and seat, even the floats. Still leaks out the same side.

Any ideas?

 

Mike Lawless

2006 HD Softail Deluxe - 2014 Triumph Bonneville
Well, there's something weird going on with this thing. On Monday morning, the thing died while on the way to work. I managed to get it home without having to push too far. It would start, run crappy, then die. Sit for a few minutes, repeat. Start, run crappy, then die.

So, this week, I had the carbs apart, and cleaned them thoroughly. They were clean to begin with, but I went ahead anyway. After a few hiccups that were the result of my plugging the bowl vent, I got 'em back on and got the thing running. It fired right up, and idled nicely. Last night, I took 'er for a ride of about 30 minutes. It ran OK, but not great. It's pretty lean. Modified exhaust, pod air filters, stock jetting....you know the drill. But, it ran. Once it got good heat into it, it behaved quite nicely as long as I didn't get too far into the throttle. I figured it was OK to ride to work this morning.

Wrong. It started right up, and I let it warm up a bit. I got to the end on the neighborhood and it dies and will not start. Acting like it's out of fuel. Tank is full, petcock on "prime" position. So, I push it the two blocks back to the house and parked it.
Tonight, I'll see if it will start and run. Same symptoms as Monday before going through the carbs. Same outside temps. Low 50s. Last night when I rode it, it was about 78°

Very curious.

At any rate, the immediate plan is to change out the vacuum petcock. But since it was on "prime" position, I would think that it would get fuel regardless.
 

Maritime

Well-Known Member
Careful if it is running lean enough you may be heat seizing the motor, and if it goes farther then that it can all go horrbley wrong, holed piston and chucks of alloy all through the motor. If you have pods, open exhaust you need to up jet or you could ruin the motor.
 

Mike Lawless

2006 HD Softail Deluxe - 2014 Triumph Bonneville
Good advise Maritime. It's not trying to tie up...at least not yet. Starter still cranks it over pretty fast.

I know full well what happens when a lean condition goes too far. I have a bunch of burned up stuff from the VW racer lining the shelves of may garage! I can't tell you how many spark plugs I've melted getting the fuel injection system sorted on that

However along that line and as much as I want to ride, I think it would be wise to get the jetting sorted as well as addressing what I think is a fuel delivery issue before riding it again.
 

Maritime

Well-Known Member
Yep, I blew up my first motorcycle because of a plugged oil feed and a clogged main jet, Cruising along at 6K rpm when it started bogging, I added throttle, thought I was getting close to reserve so flipped petcock to reserve, then a horrible noise and the bike quit, then I found DTT and learned why it happened, how to fix it, and a whole shitload more. And I still have tonnes to learn still.

Cheers
 

Shawzie

New Member
So it runs normally until a few minutes later? Try running it with the tank cap on loose. Maybe the vent is clogged
 

Mike Lawless

2006 HD Softail Deluxe - 2014 Triumph Bonneville
Did the fuel cap thing. Turns out its an intermittent electrical problem. I got it running Friday evening long enough to find out the right side pipe stayed cold and the left was hot. Checked the right side plug for spark, and sure enough, no spark.
Sooooo. 30 year old plug wires and checking connections is the next thing to get into.
This thing uses an electronic control box for the ignition. Not available anywhere. I doubt that's the problem. At least not now.
The beneficial part about this is that I'm getting crash course on how this thing works!
More mysteries to solve and challenges to overcome.
 

Scruffy

West Tennessee
The spark box can be rebuilt if needed. Runs about $15 in parts from your local Radio Shack. Pretty common even on newer Suzukis for them to fail. Suzuki electrical parts tend to make the old Lucas "Prince of Darkness" English garbage look good. My 1998 Suzuki has been down for 3 years due to the weak electrical system. Decompression solenoid relay internally shorted. So a 5 minute bypass that worked to start it turned into a 3 fried batteries in one season electrical nightmare. Still need to test the stator once everything else is finished. Bike is only a couple months from being back on the road.
 

Mike Lawless

2006 HD Softail Deluxe - 2014 Triumph Bonneville
This thing is starting to piss me off, so I just have to walk away from it for awhile.

Pulled the plug wires out. I thought I had some spares off a car project from a few years back. Couldn't find 'em. I switched sides. After routing the wires away from the frame, I actaully got both sides to produce a weak spark. Put it back together, and tried to fire it. Just didn't wanna light. On a whim, I sprayed starting fluid at one carb. She lights up for a few seconds. After some fiddling, I got it to fire on full choke for a short time. Both pipes got warm. Then it would only fart a little when cranking.

Take the carbs off. Bowls are clean. While they are off, I spray a short shot of starting fluid into the open intake port. Yeah, I know it's risky. Too much fluid and it will rev to the moon. It was a very short shot. Don't try this at home guys. It's a desperation move that really go bad.

It lit right off and ran for about a second. That's all the fluid I gave it.

So, I think a pair of coils and a set of plug wires are on my shopping list. But I'm really losing patience with these carbs. So, to keep from making a mistake, I'm just gonna back away for a little while.

Scruffy, on the control box, I have me an "outside the box" idear....

One of my race car sponsors produces a line of electronic engine control devices. What I'm thinking of for an ignition solution for down the road might be interesting. A crank triggered ignition using a box designed for a four cylinder, but elimination of two of the coil drivers inside. A trigger wheel attaches to the crank, that I have the means to manufacture here in my garage, will trigger the unit. The advance curve is built into the control unit and set via laptop. On a twin cylinder deal like this, it would be what's called a "wasted spark" type thing. It'll fire both plugs at the same time, the wasted spark would be at the top of the exhaust stoke on the "non-firing" side.

It seems simple on paper.....

But that's for another day
 

Mike Lawless

2006 HD Softail Deluxe - 2014 Triumph Bonneville
What are the opinions on a single carb for a small twin like this?
I can build an intake manifold easy enough, and there's enough room for a centrally mounted single carb like a VM30 or 32. It would seem on the surface to simplify tuning, throttle set-up, no need to balance....
 

Mike Lawless

2006 HD Softail Deluxe - 2014 Triumph Bonneville
After doing a bit of research on the single carb idea, I've decided to stick with twins, since this is an odd-fire motor. The odd fire scheme would no doubt cause distribution issues.

So, I'm gonna go with a pair of VM30 or 28 Mikunis. One little obstacle, and it's not much of an obstacle. It seems boot flanges for a 65mm bolt center are not available. 60mm for a honda is.

So, i'll be manufacturing an adapter plate from 3/8" thick 6061 aluminum flat stock. (I have a bunch) The holes on a 65mm circle will use countersunk flat head screws to attach it to the head, and the other bolt circle will 60mm to use easily available honda boot flanges.

 

Mike Lawless

2006 HD Softail Deluxe - 2014 Triumph Bonneville
I have a question about fork bearings. I've got the bike stripped down to the bare frame. With the fork tubes out, but the steerer and trees still in place, it seems a bit tight, and it seems to "center itself" in the straight forward position. Is that normal? Or are the steerer bearings hosed?
 

Scruffy

West Tennessee
Drop them and check. Mine feel kind of "notchy" right now. Plan to repack them, and while out, drill and tap the steering head vents for grease fittings. Reset, fill the front end with extreme high temp/pressure grease and forget they exist.

My 1998 Suzuki has a wasted spark, crank pick up ignition. It sucks. I want points. And a kicker. So either the 1971 Honda CL100 or the 1963 Honda CL72 (248cc kick only, dual point, twin coil parallel twin) will be moving into the fix it line up asap. I'm at the "Do I send a 16g deer slug through the Suzuki engine, or just grab it with the log grapple and wrap it around a tree" stage again myself. A motorcycle w/o points or a kicker is a waste of time.
 

Mike Lawless

2006 HD Softail Deluxe - 2014 Triumph Bonneville
Scruffy, I also think points would be simpler. Do you know if earlier parts can be retro fit? Have you looked into that on yours? Y'know I almost didn't buy this bike because it didn't have a kicker. But, with only 6700 miles on it, I couldn't let it go.

This 300 uses a "breaker plate" with two magnetic pick-ups. The trigger wheel simply bolts onto the end of the crank and uses a locating dowel. I don't know what the points cam looks like for similar engines that have points.

Thanks for the advice on the fork bearings. They were coming out anyway so I can get the frame powdercoated.
 

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