Topic: Tuning some Mikunis

[MisterKnife]

Here we go:

So installed the VM32's instead with same needle H4 and main jet. Slide is now a 3.0 with a 35Pilot ( bit rich 12.3 ) but fine for testing.
Alas. same result. sometimes hang at around the 3k mark. Blib makes it go down. If I slowly give it more gas it sometimes just goes higher and hang there

Tested compression to be sure. 105-108 range for all the cylinders. bit low but I got an engine rebuild planned in the new year.
What I previous also replaced was the intake gaskets.

I'm pretty certain that I can rule out the following.
- Jetting lean
- Air leak
- Stuck throttle slide due to carb
- Uneven compression
- Valve lash out of spec
- Cam chain shenanigans
- Timing looks to be on point, normal and advance ( maybe the springs are just done that sometimes they hang? The mechanism is cleaned and freshly lubed up and has a smooth interaction )

I again did notice that Cylinder 1 had a rich plug compared to the other cylinders. What could that be?!!

For the throttle cable I have a plastic splitter with a throw of 30mm which is enough but maybe I need a 45mm metal one? like this: https://www.bowdenzug24.com/shop/anschlussteile-fuer-bowdenzughuellen/seilzugverteiler/gaszugverteiler_rund_mit_schraubdeckel_hub_45_mm/

Anyway I'm kinda lost at this point. any pointers are welcome on what more to check

P.S.
Glad I went with the VM32's I did notice much better response on the mid to high vs the VM34's. Not a total loss.

[BomberMann650]

Things are going in the right direction at least.

Upgrading the splitter could be worth it in the long run. 
What was described as

If I slowly give it more gas it sometimes just goes higher and hang there

Problem may lie in the cable and the routing.  Though its more common to see a throttle hold up with a push-pull cable setup. 
But its still an area where a cable can twist and rub.  Pulled tight on fhe way up no issue, slacks on the way down can find a spot to bind.

Plug number 1's richness could be a misfire.  Resistor cap, wire, coil become suspect. Considering the issue isn't mirrored by cylinder 4, its not likely the intake manifolds fault.

[MisterKnife]

I think it's the total throw of the splitter. Made the slack on the bottom part as much as possible and I did notice a reduction in 'hanging' so with the new splitter coming in I'll make a new cable all in 1.25mm so has less friction in the throttle also:

https://messnermoto.com/product/motorcycle-throttle-single-pull-cnc/

this is my throttle; the mechanism looks to be working super smooth tbh;
Will report back here once I got the parts in and have a new cable soldered.

Changed my jetting to a H3 needle with a needle jet of P-8 and a pilot of 30. this is without and UFO but still have some torque wings in it. Might re-add the UFO's once that hanging issue is totally resolved, with them the startup cold need less choke which is nice.

For the Cyl1 might be a break in the cable then. Switch plugs already and it didn't move. Trimmed the cable 1/4in. No change.
So think it's probably the cable. Wanted to switch to nice coils dyna coils anyway (5ohm)

[BomberMann650]

need less choke which is nice

Depending on the ambient air temp, elevation, and particular intake solution - that may not be so nice in the long run.

Those vm chokes do supply a massive amount of fuel enrichment though.
Between the wideband meter and proper idle plug readings.  Ensuring afr at idle shouldn't be a big ordeal. 
Getting it to operate smoothly on the road however.  Thats the fun part. 

[MisterKnife]

Yeah afr is the same with the UFO discs but I think it’s due to the lack of unwanted turbulence caused by the slide that it’s just smoother on the low end. Will try it out and also report back

I’m in Amsterdam, so can’t really get lower I suppose.

Think I’ll make a build thread also as I have plenty of other stuff I want to do to this machine

[MisterKnife]

need less choke which is nice

Depending on the ambient air temp, elevation, and particular intake solution - that may not be so nice in the long run.

Those vm chokes do supply a massive amount of fuel enrichment though.
Between the wideband meter and proper idle plug readings.  Ensuring afr at idle shouldn't be a big ordeal. 
Getting it to operate smoothly on the road however.  Thats the fun part.

Switched the throttle splitter and I yet have to run into any hanging issue. Need to fix some routing of the cables they are a bit stiff atm.

She really runs great now, especially with the H3 needle. It's a more smooth / very quick power band going all the way up to the 8k. (not pushing her further after I do the engine rebuild.)

I had made a sheet with all the specs from mikuni needles/jets where you could compare them visually. blue is the h4 what I had with the p-5 and yellow is the h3 with a p-8

[BomberMann650]

Huzzah!