Finally getting around to the 550/699 project....

[tkent02]

OK, swapped ignitions back, so that should be good. Went down to the local moto wrecking yard and looked through their petcocks for the pre 1980 style with the pipes on the aft side. The only one I found had a bad oring on the vacuum valve, so it wouldn't shut off. Remembered how to give it a manual off position from several years ago and put it all together. Petcock works, no leaks, went for a short ride, it's still misfiring. Kind of an annoyance, I just want to ride it.

 

[tkent02]

OK, progress. After checking and setting the points twice, checking the condensers twice, reseting the timing twice and not improving the misfiring at all, I sat back, drank a beer, looked at the bike and listened to what it was saying. Definitely ignition it says, the mixture is close enough. Ignition huh? OK I got this. So instead of thinking about what I might have screwed up the last time I worked on to cause this misfiring, I looked at it as I would a new to me bike that was running that way. I'd check the points and condenser once, if that didn't fix it I'd check the spark plug caps. So that's what I did. All fubar. Too much resistance, took them apart, missing one the little connector springs, corrosion in a couple of them, one had been "fixed" by some PO. How it's been running perfectly the whole time it was a 550 I have no idea.

So new caps went on, new spark plugs too, just fired it up this morning. Idles nice, no missfiring. Got my jacket and helmet on, went for a little ride. Smooth as silk. Mixture seems pretty close to being right. Couple miles down the road, it's warmed up enough, open the throttle, this thing is fast now. Raining, roads are wet and there's a few rush hour stragglers around so nothing too crazy, but this ****er goes! Hell of a lot better than it did with the 550 engine!
Finally, get to an open space on the road, no cars, no cops in sight, let er rip!! Woo HOooo what an improvement, up through two or three gears, maybe four..... and the throttle sticks again. Wide open, and of course I didn't notice it until I got to the end of my open space, woo hoo indeed.

I totally forgot about that part. I need the proper CV carb throttle cable.

 

[boris.h]

Yeah, so good!
While listening to you, I can not wait to try mine. Just need to finish mine. I need again the 650 head which is slmost finished, and the exhaust (modified bandit exhaust). I think the diffferences between mine and yours will be: ported head, velocity stacks, and the bandit open exhaust. That's why I will start with bigger jets.... I'll see....But happy to see it functionnal

 

[boris.h]

which spark plugs do you use?

 

[tkent02]

Just picked up NGK D8EA, which is stock for the 650. Picking a head from the local Moto wrecker tomorrow to send off to get ported, will use that one with the 699 pistons if that group buy ever happens... Just using an old 550 Vance and Hines until I find a nice 650 4-1.

 

[Chuck78]

Sounding great Tom. I can't wait to get ours together here. I really think of the GS650E (& GS550 77-82 + 650 top) as the ultimate all-around GS... GS1000 2nd place, as it's a big beast but probably the best 70's Superbike platform. GS1100E 3rd, heavier, lost the classic styling, but wow what an advanced engine.

The 650 head and piston design is basically a 2 valve shim & bucket version of the 4 valve rocker arm head chamber / dome / port design. So no wonder the 673 makes nearly identical power numbers to the heavier 750 8v...

 

[tkent02]

Mine is way faster than my 750. No comparison. But the 750 is still jetted for sea level.

 

[tkent02]

OK, after being gone a month, finally fixed all the stupid stuff and went for a real ride. Up in the hills, around town, I like it. Good torque, pulls hard, but the main jet isn't quite right, it's OK at full throttle and half RPM, but at 8,000 or 9,000 is isn't. Misses a bit, power drops off, if you close the throttle a 1/4 turn it goes like it should... Went to look at the plugs but the tool bag on the bike still contained the plug wrench for the B8ES on the 550 head, the 650 head uses the smaller spark plugs. I think the main jet is too big, but I haven't tuned CVs in a while...
I know you have to get the main jet right first.

Out for a ride... with the correct wrench this time.

 

[roeme]

(...) it's OK at full throttle and half RPM, but at 8,000 or 9,000 is isn't.(...)

Huh, that's interesting, that sounds like my stock 550?

Begins to pull at 4-5k, dropping off around eight, and hitting a wall at nine (though that might be more because a) in my country you'll get shot on sight at these speeds and b) I have to concentrate so much on the road unless I want to kill myself, and hence do not open further).

Though IIIRC I can't open the throttle fully @5k, engine gets flooded.

Where's the redline after the 699 conversion anyway? (I presume it's dictated by how fast the valves can close/open)

 

[boris.h]

About your jetting, you said it's pretty close...could you tell us more about your jetting configuration? I know you are not at sea level but it's just to get a referenice. Thanks!

 

[tkent02]

Where's the redline after the 699 conversion anyway? (I presume it's dictated by how fast the valves can close/open)

Redline? You're kidding, right? This is based on a 550 after all.

 

[tkent02]

About your jetting, you said it's pretty close...could you tell us more about your jetting configuration? I know you are not at sea level but it's just to get a referenice. Thanks!

Jetting is lean. I'll put in bigger mains and try it again. I'll posit up what I end up with.

 

[tkent02]

Huh, that's interesting, that sounds like my stock 550?

Begins to pull at 4-5k, dropping off around eight, and hitting a wall at nine

Something is wrong, 9,000 RPM should be the start of it's happy place. Should take off like a shot after that.

 

[roeme]

So why did Suzuki bother to put in a redline at all?

In all seriousness, I'd really like to know why this particular engine is able to withstand RPMs well beyond 9500k (which is the redline on my tach).
There is a lot of conflicting information floating around.

Begins to pull at 4-5k, dropping off around eight, and hitting a wall at nine (...)

Something is wrong, 9,000 RPM should be the start of it's happy place. Should take off like a shot after that.

Well tbh my statement has to be taken with a grain of salt, since I'm still a novice, and around here we don't really have the roads (and laws) for me to really check torque at these RPM's.
I'll investigate further.

 

[tkent02]

All I know is I have been winding the crap out of several 550s for 38 years, well past the red line any time I wanted to go fast. Purposely to 10,000 or 11,000, if it hits 12,000 so be it. Never had one up so high the power dropped off, never had any valves float or anything like that, never had one take any damage or do anything but run perfectly. After 120,000 miles of this we took one apart because of leaky gaskets, all of the metal parts were within service limits, cam chain, pistons, rings, all of it.

A GS550 at anything less than about 7,000 RPM is a real dog.

 

[Nessism]

The 550/650's share the same valve springs as the larger bikes, only the valves themselves are smaller/lighter so the rev ceiling is higher. 12,000 rpm shouldn't cause any valve float issues, although the power band may start to sag due to cam timing.

 

[tkent02]

12,000 rpm shouldn't cause any valve float issues, although the power band may start to sag due to cam timing.

Yeah, you would think, but you would be wrong. The 550 cam timing is ridiculous. The main reason I am using the 650 cams in my 550/675, they have a much more normal power band, including some low end grunt. No longer do I have to go to 6,000 RPM to start out from a stop. Not sure yet what it will do up top, it doesn't have that huge kick starting at 9,000, but it still goes pretty good. I'll know more when I get the carburetors dialed in.

 

[boris.h]

hey again!
Did some acelerations that evening, the acceleration is incredible for a "650" one, I share the same point of view with you on that swap. for the carb settings, I'm too lean at 1/4, 1/8th throttle, but I think I'm close at WOT, the bike goes past 4000 rpm as a bullet --> 142.5 mikuni mains. I'm located at few metters from the sea level.

 

[tkent02]

hey again!
Did some acelerations that evening, the acceleration is incredible for a "650" one, I share the same point of view with you on that swap. for the carb settings, I'm too lean at 1/4, 1/8th throttle, but I think I'm close at WOT, the bike goes past 4000 rpm as a bullet --> 142.5 mikuni mains. I'm located at few metters from the sea level.

OK Boris, can't remember your cam or intake or exhaust. All affect carburetion. I just went from DJ 152 mains to DJ 160, seems better but haven't ridden it much, have another float problem going on now.

 

[roeme]

tkent, Nessism, thanks for the valuable information.

(...) After 120,000 miles of this we took one apart because of leaky gaskets, all of the metal parts were within service limits, cam chain, pistons, rings, all of it.(...)

This mirrors my experience somewhat and gives me confidence; I had the valve shims checked just the other day on my daily 550 (didn't do it myself because the other one isn't yet ready), unknown PO story re. servicing, 70244kms, one shim was out of tolerance, at 0.1mm.

A GS550 at anything less than about 7,000 RPM is a real dog.

Looks like I'm in for some fun. But not to further derail the thread.