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GS1100E and Mikuni 33 smoothies

  • Thread starter Thread starter Guest
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Getting close to reinstalling my carbs. Have a few pics of the process, and I?ll post one here. I?ll do the (PITA) tank cleaning routine before I get that far, and use an inline filter for awhile afterward. I?ll go through and check the valves, while I have everything out of the way. Glad there aren?t shims.

Been spending most of my time getting my 99 ZRX going, after rebuilding the stock CVK carbs, and it?s running great now. Nice to get back on a liter bike; it?s been awhile.

Once I get these two running right, I?m on to my KZ750 Twin - just ordered some VM34 carbs for it, instead of futzing with the BS38s.

A0CA9741-EC81-4AD7-8E08-E0F0D3A57D84.jpg
 
pete said:
Yep cool Greg, while I understood that referred to the cutaway I didn't think about modifying them... hopefully something I don't need to consider as that's a daunting prospect for me!
Click to expand...

If push comes to shove, post the slides over here and i'll do them for you.
 
Cheers Greg, good to know! Right now I know my needle seems to be in a pretty good position but after dropping the mains to 115's I'm still too rich up top so need to go lower yet, just gotta decide if 112.5's are enough or if I need to go 110's. The 122.5's had the AFR gauge reading 10:1 (limit of rich on it) and the 115's get to low 11's and I'm aiming for around 13, so dropping at least another 2 sizes sounds like the best next step.

I still have the idle higher than I'd like as a nice setting for the air screw still eludes me, but to be honest I haven't given that the proper amount of attention I should just yet as I've wanted to really get the motor run in rather than idling.
 
Be aware that the pilots have an effect higher up the range than you'd think. Too rich on them and you get fuel bleeding through them well into what should be the needle area. On the smoothbores - and Keihin CR's - it can be easy to go too rich on the idles to get response and pay for it with problems further up.
 
Ah interesting! What I was seeing with the needles was low 14's at 1/4 throttle, around 13 at half throttle, then 3/4 throttle and over is where it dived down to 11.

I was actually contemplating another quarter turn in on the air screws to get that 1/4 throttle area just a touch richer, but that might be too much? I can only try it and give it a go right?
 
I have 17.5's in there now, tried 22.5's when I thought it was too lean before I properly bench sync'd them but they were way too rich (even at 1.5 turns out on the air screws).
 
pete said:
I have 17.5's in there now, tried 22.5's when I thought it was too lean before I properly bench sync'd them but they were way too rich (even at 1.5 turns out on the air screws).
Click to expand...

It is starting to sound like it needs bigger slide cutaways - more air - IE leaner at that point. Once you run out of adjustment on what can be adjusted, it's time to look at the cutaways.
 
Ah ok, I've only read through the Sudco tuning manual but that's about it aside from a bit of Google searching, and understand how/when that cutaway comes into play is a little confusing to me. Cheers Greg!
 
Well I'm pretty convinced it's the throttle valves causing me grief. I spent some time with the idle adjustment and air screws and got it down to a reasonable RPM with a reasonably steady idle, but now way too rich around 1/8 throttle, and the 2.0 throttle valves would in theory make a difference there.

I'm not sure about another symptom though but I suspect same cause... if moving along with the throttle in the 1/8 to 1/4 range, then closing it to downshift or roll into a corner with engine braking, there's a big delay when I open it again before the engine responds, something like a second. If I crack the throttle even more it kicks in sure, but that's a big kick in the pants mid corner so can get a little scary. If I keep the throttle just partially open, the issue goes away completely.

So, is there a template or measurements or something to copy to adjust the throttle valves from 1.5 to 2.0? I just remembered yesterday I still have a mate's stock Kat carbs here that should only be missing the main jets, so I'm contemplating giving them a once over and installing them to let me put some time into the VM33's.
 
Sit a slide, base down, on a flat surface. It should be possible to measure the height of the cutaway with a vernier or sliding drills in as a gauge.
I assume the 1.5 or 2.0 is probably millimeters. On british carbs it's 1/16 inch per 1.0 division.

Once established it's easy enough to scribe a line at the height you want to cut to. Then it's usually easiest to use a linisher to trim to a straight line back to the original point the cutaway ended. Deburr the edges and you're done.
This is the way to raise the cutaway - making it leaner off idle.

To make it richer, I put the slide in a lathe and trim a little off the flat base at a time - thus lowering the cutaway.

I have to admit that the last few carbs I've done have all required richening in this area as they were intended in their OE use to run with filters - and I wanted to run them open.
 
Cheers Greg, that makes sense although a little tricky for my capabilities.

Definitely thinking of putting those stock carbs in while I figure out what to do with the VM33's, don't really want to give up on them but I also don't want to screw them up.

At least if I have the Kat still running without them installed I can take them apart and see how confident I feel.
 
Well I got the stock carbs dialed in and will send the slides off to Greg... and Greg when I dismantled the VM33's last night I noticed the cutaway was a lot more than 1.5mm and I measured them closer to 2.4mm. A Google showed up that these use the British measurements also rather than metric.

Also, the more I read about the arm stretching with these carbs the more I want to get them right as that's the one big difference I've noticed compared to the stock ones; they just don't have that same pull when the throttle opens.
 
Oh, I also forgot to ask... any way to tell if the jet block gaskets are good or bad and any tips on how to safely remove/replace them? They look a bit old to me but given the recess they're in I've not tried to remove them and check them out just yet. I figure now's the time to replace them if it's necessary though as I've read bad jet block gaskets will cause constant idle issues.
 
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