All tuned and no fizzle

AussiXS

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I have a Japense import 1978. XS650 SE with the Vin 447901xxx. I bought him from Old Gold in Londonderry, in Australia. It was running alright when I bought it but I drove it up the road and back so nothing definitive. I have striped it down to frame to repaint and turn it into a brat/cafe, every bolt off and back on . Now it's all assembled and she is looking good and all is going fairly well ,I am at the final tuning stage. So, I did the cam chain so it was flush. Adjusted the tappet to 004 on intake and 006 on exhaust and did static timing on the points, they were pretty close. However, when I attached a light on the bottom point it didn't shine bright as the top set of points. I moved the copper tang on the carbs when I first got them to something crazy like 32mm and the thing ran mega rich! I now dropped it down to 24mm. So, I have her started and idling and it drive up my drive way but sometimes it backfires and pops the pod filters off and smokes from the carbs. If it drops too far in revs it will stall. I can't take it for a big ride because it's u nregistered, so it's just static testing for everything. (Except the ride today, where I broke down, I needed fuel, so I filled it up and it took like 30 sweaty kicks to get it started after that)

My issues:
1. When I put the choke on, it stalls right away.
2. When I give a quick throttle it stalls, but when it's warm it's fine.
3. When I am in first gear, I get upto about 20km and and it just kicks in and gives me a speed boost. Like a turbo kicks in a car. Kinda scary!
4. I have an oil leak that looks like it's coming from the starter motor. Can I take the starter motor off without taking the engine from the frame? IS that a common place or could it be something else?
5. Why does it backfire?

Are all these issues (besides the leak) timing issues, point issue or carb issues? It's so hard to tell because they are all related. There are also so many years and types of theses bikes that getting the right specs for my bike it hard. I did not mark down where the tappets where at but I adjusted them smaller.

I just went for rego and he didn't pass it because of the leak, then I got pulled over by the cops on the way home. Lucky the guy was feeling pretty generous so just told me off, but I had to push it back to the service station and left it there for the night. What would be the first thing you guys would do?
 
The first thing I'd do is to hitch up the trailer and bring the bike home! I have no idea what you've done to your carbs, but if you initially raised the float level to 32 mm. you would have lowered the fuel level, resulting in a lean mixture, not a rich one. If I had to make a guess it would be that you have one or more bad floats and/or float valves. Bench testing and inspection will tell you if those things are problems; inspect before you buy parts, and if you do have to buy parts get the right stuff by Mikuni, not Chiwanese knockoffs.
 
the poor thing has spent the night with someone else! Thanks for the tips. I have taken the carbs apart and everything seems fine, I bought new kits but decided to keep the majority of the original because it was fine and operating. Plus I cleaned with carb cleaner and air, Nothing is blocked.

Anymore tips on what you would try? Do you think the tappets are the right distance?
 
.004 and .006 is the general consensus on the tappets. Adjust the brass in the carbs to factory spec and leave it there. Your problem lies elsewhere.
 
it backfires and pops the pod filters off and smokes from the carbs

Assuming your carbs are stock CV units, I believe your "pod filters" may be part of your problem.
And maybe you should check your ignition thoroughly. Just not static timing, but also the advance unit. The weaker test light indicates bad breaker points, or a poor connection somewhere between battery and breaker points, i.e ignition switch, kill switch, bullet connectors either side of coils, all wires etc.
Voltage measured across CLOSED points should be minimal in any case (measured with ignition on, of course)
 
Yes, you need to check your timing with a timing light as the bike idles. Static timing is just a "ball park" setting and not always accurate. Also check the cam chain adjustment while the bike idles. Observe the plunger in the end of the adjuster bolt. It should bounce in and out slightly, like 1 or 2mm. If it doesn't move at all, your setting is too tight. If moving more, your setting is too loose. You can set the adjustment as the bike sits there idling. Turn the adjuster in until the plunger movement stops, then back out until you get the small amount of motion needed.

The valve specs for your '78 are .004" on the intakes and .006" for the exhausts. Sometimes using .004" on the intakes causes a lot of ticking. If that's the case, close them up to .003". I know, it's only a .001" difference, but it can make a big difference in the noise level.

The way your bike comes on hard near 20 MPH in first could indicate your advance unit is sticking, not advancing smoothly as it should. It and the advance rod that it mounts to most likely need to be serviced (cleaned and lubed).
 
I still haven't been able to get a van to pick the bike from the shop, so I can't test all theses ideas and get to the bottom of it. Thank you all very much! I will let you know how it goes when I get her back.
 
So I'm back! Fixing this bike has been a nightmare! the leaks were sorted with a new gasket and seal kit, I didn't do the engine gaskets tho. Had to take the engine off, don't want to do that by myself again!

The issue: i rode it to rego and it worked....just! (He still passed it tho, yay. His problem was the leaks). It has barely any acceleration, it rides but not like a 650. In first, it powers on slowly then kicks in with speed hard as I get to second.

Once it's still, it starts fine and revs drop fine and seems like the perfect bike, but it stalls wherever I touch the choke.

What I have done to fix:
5 twins you were bang on the money, the advance unit was as dry as the Sahara! I lubed that puppy up and that is when I had real issues, it wouldn't start. The timing was well out of whack. I think causeThere was grease all over the the points side. I took it all off to clean and attempted to redo the timing. Nope!

Timing:
I did static timing with light bulb on top right points. The light fires way after the F Mark, it fires around the bottom left line. The points plate doesn't more far enough to get it to the F Mark. What could that be?

Carbs:
I now have those Ramair foam filters, which look great but I haven't changed anything on the jetting, do I have to, as it runs pretty well? Just not a lot of acceleration once it's moving, it's alright but not a lot of guts. now that I write this I'm thinking it means I probably need to Jet it. Where do you get jets in aus? Or could these issues just be timing?

I just want to ride this thing! I bought a new bike for a project, a 2 stroke TS125 cause I thought the problems were over. Lord help me!
 
Here is a picture of where the light fires
 

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You're firing at or near the full advance mark. You said you lubed the advance unit but did you lube the advance rod that runs through the cam? You have to remove it, clean the grooves in the bushings on each end of the cam, and pack them with fresh grease. As the RPMs increase and the weights on the advance unit fling outward, that turns the advance rod a little bit. The points cam is attached to the other end so this changes when the timing fires. If it hasn't been lubed, your advance rod may be stuck in the full advance position. Here's the grooves in the bushings in the ends of the cam .....

GreaseGrooves.jpg


Here they are packed with fresh grease .....

GreaseGroovesFilled.jpg
 
"You're firing at or near the full advance mark. " - Is that a good thing? Before I took it all apart, the timing mark was firing bang on, with my static test.

On this image have you removed the seal and packed behind that with grease?

All I did was slather the grease all over the rod, pulled it in an out at few time and put it all back together on both sides.
 
You needn't remove the housing with the seal. I just had it off because I was replacing my rocker shaft end caps with the stainless Allen ones from Mike's. All you need do is pull the rod out of the head. Take the little disc off the advance side and pull the rod out from the points side. There is another issue, an alignment issue when you reinstall the rod, but I think your timing would be even farther off if you got that wrong (180° off). But, it's worth checking I guess. There's a slash mark on the little disc and one on the advance unit backing plate. They should point to one another, or very nearly so (yellow arrows) .....

CorrectAdvanceInstall.jpg
 
Yes, I should have mentioned, I did start it after assembly and the timing was so far off it backfired HARD! I assumed I put it back together wrong. I then saw the lines and aligned them on the advance side. Is there a correct way to put the cam on the points side on, maybe I did it backward? I put the thick bit against the engine, if that makes sense.

One other thing I didn't mention, was that after I lubed it up I was only firing from 1 cylinder, I thought it might be the grease on the points. But maybe its something else?

So bloody confusion! I appreciate your help!
 
Yes, the shoulder goes in, towards the engine, so it sounds like you got it right. You do have all the little locating pins in place, right?
 
If the locating pins are the on the rod and where the cam slots into, then yes.

It's so weird! Nothing changed but the points adjustment. Where should the points gap be set? I have been doing 14thousandths.
 
Besides the two locating pins in the ends of the advance rod, there is one more behind the advance unit that locks it on the cam in the proper position. If you had the advance unit off when you cleaned and greased it, maybe you didn't get it back on in the right position.

The points gap spec is .012"-.016" so at .014" you should be fine, right in the middle of the range. But, if the points are used, sometimes you need to set them closer to or at the minimum spec. Points develop pits in their contact faces as they're used. The spark jumps between those pits. You can't measure that distance with a feeler gauge. The gap you think you're setting is actually larger because of those pits. Really, the only accurate way to set used points is with a dwell meter.
 
So I think I have a gremlin! I wake up and turn her over and bam starts fine! Timing still fires at the far left mark but it works.

I took it for a ride and it still surges. I am going to lube up the advance unit more. Do you think it could be the carbs?
 
Revelations have come about! Instead of redoing the advance unit I took it for another ride, I can't keep off the thing! Anyway, turns out the surging is only in first gear, not even if I shift early. What do you've think it could be?
 
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