Suzuki 2 Strokes

Well my ne 550 is proving to be impossible to tune. I can get it to idle smoothly, but the main problem is it won't return. Sometimes comes back to 2.000 and the slowly comes back to idle (10-15 sec). Other times it will return to 2,000 and the begin to climb. If I kill it and the restart it. it will be at idle again. Go ahead and let it return to 2,000 and bring it ti idle with the stop screw. Rev it again and it falls off and dies. Reset the idle with the stop screw. Nice 1.200 idle. Rev it up and it hangs again in the 2500 degree range. Might come down, might go up. I have had the air screws all over the place. Stock 1 1/2, 3/4 and 1. It definitely affects it but, it cures nothing.
There is no reason this bike shouldn't run perfectly. I'm beginning to strongly suspect an air leak as it seems to be all over the place no matter what I do to correct it with the air screws and the idle stop screw. What really gets me is it will hang at 2,500 - then I kill it - then restart it and it runs at 1.200 just the way I had previously set it.
Does this sound like an air leak? Would it be most likely air box to carbs or carbs to cylinder? Remember I omitted the SRIS and blocked the intake fittings with vacuum caps. I"m thinking that one of those blew off and maybe that's the air leak. No matter how I angle my mirror, I can't see them (the caps). I need to wait till it cools off and try to see them again.
Thoughts? Suggestions? I'll report the SRIS block off caps if I can ever see them

If you have stock pilot jets and the carbs are clean and there are no leaks, you will be able to make it stall by winding the pilot air screws fully home or almost fully out, possibly both. As you say, the bike is lean - too much air from somewhere!

If the pilot air screw doesn't do it, agree you have a leak elsewhere and the job will be to find it!

Mike

That's such a tough one. Are leaks could come from so many places. Crank seals, carb to cylinder boots, cylinder base gaskets. Not a air leak if its from the carb to airbox, it may be leaking but its still measured air. I would say if it was a sris cap it would be a substantial air leak. But have to check everything. As always I'm sure the carbs were cleaned and then cleaned again. Be sure the pilot jets were screwed and seated all the way down. Maybe a leaking choke plunger valve not seating 100%. That would cause a possible higher rpm at times. Were the emulsion tubes pulled out of each carb and cleaned and cleaned again. As far as intake boots I would assume you put new Suzuki one's on as the old ones would be like a rock. Good luck with your search, If I can think of anything I'll post back. Let us know what you find..

If the crank seals were bad, wouldn't there be clouds of smoke? There is a little smoke from the left bank at start up, but that quickly goes away. Then there is no smoke at all. That really bugs me. I know I saw air bubbles moving through the lines when I first started it up, but I'm worried about the thing self destructing. I say that because there is a strong metallic smell after running,. plus it gets very hot very quickly.
I think I'm going to remove the air box end caps and filters. I did oil them and wrung them out really well, but I don't know if it might be choking it. I am also going the set the oil pump to deliver more. The metallic smell really worries me.At this point, the bike fires up instantly - even after sitting for 2 full days. You can't even hear it cranking as it fires as soon as you touch the button
Also in error, I bought KGK B7's instead of B8's. That could have something to do with the heat issue. I need to correct that right now!

That does sound like an air leak, but I would start by checking the static synch of the carb bank. Open and close the throttle and check for a hanging slide. You may find one of the linkage springs missing allowing one cylinder to close late.

If they are perfect, the next step would be to run the engine at idle and spray starter fluid at the carb boots and see if the revs rise. The safer gentler version of that is to use soapy water and check for bubbles but to do that right, you really need to blank off the exhausts and add a few pounds of pressure.

I have an RZ350. When I bought it, the crank seals were shot. Evidence was the same exact issue you point out. You could never balance the plug readings if the air adjustments were the same. So, you have to adjust the air screws based on plug readings only if you choose to run it without replacing the crank seals for example. It takes several trials to dial the air screws in to get descent or close to equal plug readings. But, the air screws will be no where close to adjusted the same. That worked for me for a lot of miles. Bike easily started, no running issues, etc. But, eventually the seals will get bad enough that the cylinders are starved of oil, Or the pistons seize. Call me an A-hole for pointing it out. But, it's the truth. You can't accurately judge the condition of crank seals by how much a pipe smokes. But, it is something to use as a visual indicator though. I've been through crank seals needing replaced twice. These indications were the same both times. How old are your intake boots ? Double check for cracks on the air box. It's very difficult to get a bike to idle correctly when the seals are bad. Especially, after the choke is open/motor is warm. In my experience nearly impossible to get a proper idle once the bike is warm.

You mentioned to me your using aftermarket handlebars. Under that circumstance, it could also possibly be the cables. I'm also using aftermarket bars and as I'm sure you know you may have to reroute the cables and adjust them several times to get everything right. Another thing I would check. After you remove carbs from letting them soak in Berryman's, etc. to install. That carb cleaner for example will leave a yellowish sticky film on the interior no matter how well you rinse them. Most carb cleaners will leave a similar film and cause the slides to hang up slightly. If you spray the intake of the carbs with PB Blaster,etc. with throttle completely shut the slides will free up. I would check that first. I recently had a similar issue and after installing carbs. The slides were welded in place until I sprayed them.

Those are obvious. No sticky slides and no cable bind. The way these carbs are made, you really can't have a sticky or lazy slide as the pulley shaft arms push them down as well as lifting them. It's all or none. I can get it ti idle. It idled for 15 minutes when I first got it going. My problem is it won't return to idle after reving. Might come back to 2500. from there it might slowly fall bak to idle in about a 30 second span. Sometimes it will come back to 2500 and slowly begin to rise. If it's running at those speeds and I kill it and start it right back up, it idles just like it did before. This is without touching anything. Just off and back on. From all I have read over the years, this points to an air leak.
And what is it with these 3 cylinder twins?. When I built the buffalo, I had trouble with the center cylinder not running. RedZone only runs on 3 when you get the rev's up,otherwise the center doesn't run. This bike is the same way. Good hot spark, ample fuel and the center does not run. Only at increased RPM. The motor should run on the center all by itself. That has never happened on the last 3 triples I have been through. Very reluctant centers on all of them. You would think a guy could get lucky once in a while

Coyote wrote:Those are obvious. No sticky slides and no cable bind. The way these carbs are made, you really can't have a sticky or lazy slide as the pulley shaft arms push them down as well as lifting them. It's all or none. I can get it ti idle. It idled for 15 minutes when I first got it going. My problem is it won't return to idle after reving. Might come back to 2500. from there it might slowly fall bak to idle in about a 30 second span. Sometimes it will come back to 2500 and slowly begin to rise. If it's running at those speeds and I kill it and start it right back up, it idles just like it did before. This is without touching anything. Just off and back on. From all I have read over the years, this points to an air leak.
And what is it with these 3 cylinder twins?. When I built the buffalo, I had trouble with the center cylinder not running. RedZone only runs on 3 when you get the rev's up,otherwise the center doesn't run. This bike is the same way. Good hot spark, ample fuel and the center does not run. Only at increased RPM. The motor should run on the center all by itself. That has never happened on the last 3 triples I have been through. Very reluctant centers on all of them. You would think a guy could get lucky once in a while

In reference to the center cylinder not firing like it should. Tweak the timing a hair on that cylinder only. If you'd like you could borrow my dial gauge for a while. Just pay shipping. A dial gauge easily and accurately allows you to inspect how far advanced or retard you tweak it. Saves a lot of time and guess work too. Just by tweaking the timing a few millimeters a cylinder can pick up spark or drop it. Depending which way you go. Advance or retard. Sometimes wires in the connectors leading to coils get pushed out of sockets slightly also if not locked in tight. Causing bad contact. Had that happen once, not allowing a cylinder to fire. Timing is usually the culprit though in my experience. Or a subpar battery. But, you know that.

Coyote wrote:Those are obvious. No sticky slides and no cable bind. The way these carbs are made, you really can't have a sticky or lazy slide as the pulley shaft arms push them down as well as lifting them. It's all or none. I can get it ti idle. It idled for 15 minutes when I first got it going. My problem is it won't return to idle after reving. Might come back to 2500. from there it might slowly fall bak to idle in about a 30 second span. Sometimes it will come back to 2500 and slowly begin to rise. If it's running at those speeds and I kill it and start it right back up, it idles just like it did before. This is without touching anything. Just off and back on. From all I have read over the years, this points to an air leak.
And what is it with these 3 cylinder twins?. When I built the buffalo, I had trouble with the center cylinder not running. RedZone only runs on 3 when you get the rev's up,otherwise the center doesn't run. This bike is the same way. Good hot spark, ample fuel and the center does not run. Only at increased RPM. The motor should run on the center all by itself. That has never happened on the last 3 triples I have been through. Very reluctant centers on all of them. You would think a guy could get lucky once in a while

Try using the carb sync method described in the early model service manual. You short one contact point and sync two cylinders equally. I just remove one spark plug cap and use a spare plug in the open cap. Following the sequence is crucial.

Coyote wrote:Well my ne 550 is proving to be impossible to tune. I can get it to idle smoothly, but the main problem is it won't return. Sometimes comes back to 2.000 and the slowly comes back to idle (10-15 sec). Other times it will return to 2,000 and the begin to climb. If I kill it and the restart it. it will be at idle again. Go ahead and let it return to 2,000 and bring it ti idle with the stop screw. Rev it again and it falls off and dies. Reset the idle with the stop screw. Nice 1.200 idle. Rev it up and it hangs again in the 2500 degree range. Might come down, might go up. I have had the air screws all over the place. Stock 1 1/2, 3/4 and 1. It definitely affects it but, it cures nothing.
There is no reason this bike shouldn't run perfectly. I'm beginning to strongly suspect an air leak as it seems to be all over the place no matter what I do to correct it with the air screws and the idle stop screw. What really gets me is it will hang at 2,500 - then I kill it - then restart it and it runs at 1.200 just the way I had previously set it.
Does this sound like an air leak? Would it be most likely air box to carbs or carbs to cylinder? Remember I omitted the SRIS and blocked the intake fittings with vacuum caps. I"m thinking that one of those blew off and maybe that's the air leak. No matter how I angle my mirror, I can't see them (the caps). I need to wait till it cools off and try to see them again.
Thoughts? Suggestions? I'll report the SRIS block off caps if I can ever see them

Hi Coyote, I was wondering if you ever solved your erratic idle speed on your 550 that you posted here back in June. The reason I ask is my 77 380 is showing signs of the same problem. The bike runs well and idles ok at 1100 revs until it occasionally suddenly decides to creep up to 2000 revs and then drops back down again after a few seconds. I can drop the idle speed quicker by slipping the clutch in gear. I've done all I can think of, New inlet boots and clips. Cleaned carbs several times, even replaced the rubber boots on the top of the carbs to eliminate any air leaks. Any Ideas on the problem will be a great help.

My bike is still apart. Took it apart to chamfer the ports. That's done, but I have made no progress putting it back together. I need someone to compress the rings while I drop the cylinders back on. The only helper is my son. He has his own life and things to do, so I don't press it. I can assemble the motor by myself on the bench. I did exactly that on RedZone. However it's a totally different story with the motor still in the frame. Plus it's been mega hot. Only the past 2 days have cooled off, but that won't last. This a one of a kind area of the country. Blistering hot in the summer. Winters are generally fairly mild except for the occasional horrific ice storm. Then we get tornadoes in the spring. Now we're even having occasional earth quakes. These are man made by the money hungry greedy bastards setting off explosions deep in the ground in an attempt to make the earth bleed more oil.

Bend a tin can around the piston to compress the rings, with a tyrap or similar around the entire thing. You should be able to get the barrel over the rings then. You used to be able to buy ring compressers like that that actually went round the piston and you could bolt them around the piston to make them as tight or slack as you liked.
HERE'S the very thing - cheap too. (clicky linky)
I'm sure they are available over your side of the pond too.

Must admit, I put the barrels on my 550 fairly easy - just make sure the top ring is located in the peg and ease the barrel down slowly, same with the bottom ring and the barrel will slide straight down.
Only mild swear words are needed!!
Everything really well lubed and it's straightforward. Smokes like a just lit campfire when it eventually fires up, but I over oil everything 'just in case' anyway.

Coyote,

Like Alan, I found it easy to get the cylinders on with the motor in the frame. It helps to have thumbnails to close up the rings one at a time. Middle pot first. If you find this hard then please don't try a 750 yet. Getting that big lump of a block on the first time, with the motor in frame, wasn't fun. I had help from someone who'd done it before.

Cheers,
Mike
ps: my own re-rebuild is waiting on its crank but the cylinders have been nicely chamfered this time before plating and I can feel the difference.

I DID IT! i DID IT!! Put the jugs back on all by myself. Wasn't that hard - except for working in a vary cramped garage. Did the center first - naturally. With each cylinder I put the piston near the bottom of its stroke. That kept them from rocking all over the place. Marked the pin location with a sharpie. Positioned the rings then set the cylinder on and gently rocked it back and forth. Didn't even compress the rings with my fingers. I just let the weight of the cylinder work for me. Rocking like that, the bevel at the bottom of the cylinder compressed the rings without nay outside help. The whole ordeal only took about 30 minutes.
I need to know if this is true. I was told once before that if the ring gap is not over the pin, (pin under the ring)the cylinder will no go on. True?