Trouble Getting Going

[ChrisK]

My guess, since I have not read what he wrote is fuel and synch first because how are you going to run it on the dyno if you can't get it to idle?  Then back to idle when you get everything else correct.

Have you done a compression check, valve clearance, checked for vacuum leaks and checked for proper timing yet?  This is a must!

That makes sense.

In an earlier post I stated I don't have the proper fitting to do compression. I have the gauge, just not the part that screws into the cylinder, working on that. Valve clearances are good. No vacuum leaks. Timing set.

[ChrisK]

Okay, I just tried 5th needle clip, 165's, 60's, 1 turn out on fuel, and 1.5 turns out air.

It was pretty good, actually. I believe the main jets are pretty well sorted out. It pulled well to 100 mph in 5th gear into a 25-30 mph head wind.

There are a couple of things I would like to sort out. First, I still have that sharp vibration while taking off from a stop. Second, it didn't quite feel as smooth as possible cruising with no changes to throttle. Finally, it didn't die at idle, but it didn't sound good.

I'm going to adjust the fuel screws according to Burns' tutorial, then take it on another ride and report back.

[ChrisK]

Okay so I initially went a half and then 1 turn out on the fuel screws while it was idling and it seemed to be worse. So I screwed them all the way in to see if it would stay running. It did and it seemed to idle faster. I took it for a quick ride and while stopped at a light it did idle much better.

However, I still have the quick vibration and now it was lagging at throttle pickup pretty bad. What I mean by that is coming into a turn at no throttle, then when I tried to pickup the throttle it dove on me. To me that says too lean. I'm going to give half a turn out a try.

[ChrisK]

Okay tried the half turn out. Pretty good idle, but I think it was worse than the idle with then all the way in. I still had the sharp vibration. It was still diving on pickup, but it was slightly better.

The interesting variable to that is I keep forgetting its 33 degrees outside right now. 20 degree difference from yesterday, and potential 20 degree difference from tomorrow.

According to Burns, if you're more than a turn in on fuel mixture to get your best idle, it's time to try a different slow fuel jet. I believe I am so I'm thinking I might need to order 57's, the middle ground to the next size smaller I have at 55's. Additionally, the slow air screw affects performance at higher revs and from closed to 1/10th throttle. That closed to 1/10 is where I feel like I'm having problems right now. So maybe if after dialing in the next size down in slow jets the problem still persists, I'll fiddle with the air screws.

What do you guys think?

[koko64]

Yes
Sort the idle slow jet by trying the 58/57 and get the ims in spec of 1-2 turns and idling strong with good low speed/cruising running. Maybe back to 55 if needed, but see first with the 57/58.
When thats sorted, then fine tune with the SAJ screw. Keep an eye on plug colors.
Needle and MJ require experience and/or dynos. MJ to be legal requires dyno or some educated guessing and using other folks data from dyno tests.
Pardon my spelling, I was checking in on the phone.

The needle and MJ must be quite close to leave for awhile. How close was speeddog right up?  Buy him a drink. That saved a lot of trouble for sure.

Good on you, you are getting there.

Once that idle is sorted, and slow jet with it, the trickiest part of the circuit. The area where the slow fuel jet, slow air jet, needle root diameter and IMS (and even the needle pos-n to an extent) all overlap; the 1/8 to 1/4ish throttle transition and the trailing throttle you mentioned.

Very fine tuning of the SAJ screw can fix this if you have the slow fuel jet and IMS correct, and also have the correct needle root diameter Brad mentioned. I had to change my needle because no amount of tuning this area was 100% to my satisfaction and I tuned around it to about 90% and rode that for months. But the 10% was breaking my balls . I suspect some people would be fine with that but I knew it was there.

It is unlikely you will need to change your needle with a pretty stock motor. I agree with Howie that the plug looked rich and that probably means going to the 58s or 55s. Howie is also correct that it's good to be sure of your motor's overall condition in case some anomaly creates a tuning problem that sends you on a wild goose chase. He was very Miyagi San reminding us to not forget the fundamentals. you'll end up with 58s and a more open SAJ or 55s and the SAJ a little more closed (probably).

The thing about the SAJ screw is that you can adjust it to suit your own taste and riding style, and not just for it's interaction with the slow circuit. The SAJ screw lets you fine tune that tricky area, but it also allows you to opt for smooth Vs snappy response off a closed throttle. There can be some personal preference with this.

[ChrisK]

Im concentrating on the IMS, SJ & SAJ as you can test them at legal speeds. Needle and MJ on tne highway when overtaking can be done to a certain extent if you are experienced or prepared to p,ay.

Is that in response to my post about running it up past 100? Or did you not see that one?

Either way, I live in flatland Illinois, there are hundreds of long, straight, flat, no-traffic roads surrounding me. It's normally an unfortunate thing. But for testing mains it's alright. Wish I had access to a dyno though.

[koko64]

I was on the small phone, I'm on the laptop now. You have the room to sort the latter jetting for sure. I have to use a dyno where I live, or get tazered and bike crushed I have a mile and a half long and very steep mountain road that would be a great dyno, if I was so inclined.

Luckily, the tricky circuits are in the lower speeds and transitional throttle range.

[ChrisK]

More bad news. Took the bike out, 20 degrees warmer today and it ran like crap. Felt the whole time like I was dropping a cylinder, so I immediately checked the plugs when I got back to my garage:



What do you guys think the problem is? The carbs are tuned exactly the same, and I've even put a manometer on the intakes and gotten good synchronization readings.

Does this look like an electrical problem to you guys? No spark in one cylinder? Way back at the beginning of this thread I didn't have spark in the vertical cylinder. Now the horizontal cylinder is the one that looks rich. Or do you think the horizontal got fouled and so it turned out drenched in black like that?

I NEED TO ADD, I THINK THE PROBLEM GOT WORSE THE LONGER I RODE.

[Howie]

The fouled (black) plug...powdery, oily or wet and smells of gasoline?

[ChrisK]

The fouled (black) plug...powdery, oily or wet and smells of gasoline?

I smelled it when I pulled it out and I thought it smelled like gas. Yeah I guess I would call it wet before I called it powdery or oily.

I ran out of time before I could check for spark. Had to be somewhere.

[ChrisK]

I have spark on both cylinders but one seems visibly brighter than the other. The duller spark has a purple tint to it while the brighter one looks more white.

EDIT: put fresh plugs in and their spark is the same. Any guesses on why I fouled a plug? Current setup is 165 mains, 60 slows, 1/2 fuel, and 1 1/2 air.

[ChrisK]

Switched to 155 mains thinking it was richening everything, bike wouldn't even idle. I'm going to now switch to 160's and see what happens.

[ChrisK]

ANDDDDD half of my main jet just twisted off inside the carb. GREAT.

[ChrisK]

I guess I got pretty lucky. I was able to push a small screwdriver into the end of the broken piece and get it to screw out.

Back to 165's I guess. Any suggestions?

[ducpainter]

I'd suggest figuring out why you have a weak spark before you drive yourself nuts make the beast with two backsing with jets.