Jetting this Bike

[Striker1423]

The best of topics that EVERYONE LOVES.

Motor:

Timing set to 1.8 (Dial-indicator set only. Janky timing light is janky.)
Exhaust is Street Retro JL's. (Lomas himself said they were designed to mimic the stock exhaust in an email to me.) Although how that supposedly works confuses me.

The carburetor specs I started with were as follows,

Stock Mikuni VM28's that are Dave F Modded (drilled out, not tapped.)
Needle in 3rd position.
40 pilot.
270 main.
Air screw turned out to 1.5.
Idle screw at 1.25 in. (1400 RPM idle.)

Where I ended up to get smoothest, fastest idle was as follows,

40 pilot (3 turns out)
37.5 pilot (2.25 turns out)
35 pilot (not 100% sure just yet. Seems to like 1.5?)

I'm just having a hard time tuning the pilot circuit by ear. The throttle is settling into a steady idle off a snap open fairly quickly, but it is lagging slightly as compared to what it was with the 40 pilot (almost instant return to idle). If this is the case, something was definitely off with the 35 pilots before at 1 turn out.

So, are there any similar setups that are a better baseline to go off of? Anyone else end up higher than a 35 pilot with stage 1 porting, etc?

[Striker1423]

I'm thinking I'll try and replicate the motor purring along with a 32.5 pilot next. It seems to like 2 turns out on a 35. I have a feeling a 32.5 might get me closer to 1.25 or 1.5 turns out.

[1976RD400C]

I think you can feel how the pilot circuit is working by riding it and just barely cracking the throttle open. If it is too rich it will be cackling and four stroking. Did you ride it with a 270 main, that seems kind of big with stock carbs?

[Striker1423]

I have ridden it around the block. Can't hoon on it too much in the sub. But, I'm positive 270 is too big. Just, how much so is the question. I', trying to be methodical with my tuning though. I'd like to dial the pilot circuit in first, then attack the mids, and finally the main. I'm following the Kevin Cameron article as best I can. Just, I've never quite approached a fresh engine as meticulously before, so that probably explains a few of my initial troubles.

[m in sc]

run a 32.5. if oyu cen get it to die at idle all the way in, and idle consistenly and smoothly after warm with a non hanging return after a snap of the throttle, and the airscrew is at 1.25-1.75 you're good there. if you have power issues going off idle, look at clip position.

you hit some WOT to test the main? id imagine with a dave f a 220-230 would be tops.   

[Striker1423]

Yea, 32.5 is next. One thing, I'm getting awesome at removing and installing the carbs again. Almost a year without touching it had me rusty lol.

[Greaser Greg]

A couple of weeks ago I taught  my twelve year old daughter to do it for me, cuz, well, it got old.

[RSW46]

I had an issue with the idle not settling down very fast on my 350 not long ago and it turned out that I had dirty uniflow air filters. Once I cleaned the filter the motor settled to idle after a blip as it should have. I am running 32.5 also. I will not mention how many times I cleaned the carbs before I cleaned the filters and fixed the returning to idle issue.

[Jspooner]

you hit some WOT to test the main? id imagine with a dave f a 220-230 would be tops.   

yes^^^I'm thinking even smaller, but this is where I'd start.

[Striker1423]

Ok the 32.5 pilot is in. Both jets were clogged. Think I got sold some old ones. But, anyway I got the bike running. It seems to run ok at 1.25 turns out. Takes throttle but slowly builds. I put a 250 main in and maybe that's one of the reasons it builds slowly, but I'm tired. Had them carbs out 5 times today lol.

EDIT:

The bike won't really die with the air screws turned all the way in. Now I'm a bit confused. I'll try warming the bike up later and seeing what happens.

[m in sc]

if it goes super sluggish though its fine. doesnt nec need to 'die'

you nee dot work on the needle if the revs build slow. then focus on main.

try one clip richer (4th), see if it gets worse or better. if better, you're prob good. if worse, then go back 2 settings. (which would land at the #2 clip, or 1 lean).

[Striker1423]

Ok, I'll work with the needle next. See if I can improve the acceleration. I see that the slides can be different as well from the article. Did mikuni ever make different slides for these carbs? Anyone ever have to change the slides?

[Striker1423]

The needle change one richer (4th position) fixed the throttle hesitancy. Now I can work on the main jets. I'll warm the bike up and use the iridiums to get me home etc. I have 5 sets of B8HS plugs I can use to jet with.

[Striker1423]

Idle surging at lights. Gah! Hesitates to accelerate until past 1/2 throttle still. Will go one richer on needle (5th position). But, before I do that. I have my air screws set to 1.25 and the bike hunts for idle at 1500 to 2000 RPM. I'm thinking lean on the pilot. Seems strange to me.

EDIT:
Also, I have this weird clanky noise every once in a while. I'm running 93 octane off the pump. So, I don't know. I'm too paranoid tonight to do anything about it.

[Striker1423]

OH HELL NO.

I know why its making this weird rattle noise. The oil pump pin fell out. Why? Because I failed to put the pin holding washer on the pump thinking I wouldn't need it right away.  Pulled the cover off and the pin fell on the floor.

New Baltimore Fishfly Festival is tonight and they have a beer tent. So... I'm going now.