920cc GS750 build - head gasket, deck height, valve sizes, cams, ?'s

[Chuck78]

I posted that earlier but it was of those times where I couldn't get any forum page to load, only getting an error page saying that the server is too busy. Looked like it posted to me, strange, not here now.

I also mentioned in the missing post that the needles for the VM26 carbs probably won't work on your BS32's because the 32mm tall CV carb venturi's are taller than the 26mm vm's. You'll need to look up height on your stock spec needle, or total length rather, and find one of that spec with notches in the same spot, and a skinnier taper.

I also had mentioned that the Mikuni needles run like $14-17 each, so a Dynojet kit for your specific carb and bike will give you some agressive tapered needles and extra jets to play with for a slight bit more cost but definitely will be a good taper needle with no guesswork, very minimal chance of getting their needles and saying "whoops, way too rich now!" as compared to picking a Mikuni needle and then the harder part, trying to find one or find out what bikes they came on and source that. Some of them are darn hard to track down. Cheaper route would be Mikuni's with a lot of research and knowledge of exactly what kind of taper your bike setup is going to run best with, but there are a lot of variables there.

[tirebiter]

Yes, it's not easy to make the correct choice but I have done considerable work with similar carbs on automobiles so I already have a good idea of what's ahead.

One thing that worries me already is an apparent discrepancy. I measured my 5D50's that are in the bike as stock. The chart is nowhere near what I measured.

Apparently I need to study more on how to look at the chart ! Definitely off-topic here. I'll start a new thread once I figure out what the chart is telling me ... or not.

[Chuck78]

keep in mind that unless you want to change your needle jets also, keep the upper part of the needle you are shopping for very near the exact diameter. any skinnier at the thickest points at the beginnings of the taper, and you will run very rich at low throttle/slide opening positions, and it will not be adjustable in any way other than changing needle or needle jets. a skinnier needle or a larger needle jet do the same thing, more fuel. A wideband o2 AFR gauge setup for $160 really saves a TON of tuning time (doing plug reads and plug chops), hassle, and guesswork. the initial diameter is the most critical thing to get correct, as you can move the taper around by changing the needle height, but you can't change the base diameter to make it run more lean. The incremental differences in diameter are so tiny that sanding one with fine grit emory cloth would be far too inaccurate to try and richen a lean idle and low throttle openings condition.

[tirebiter]

Chuck78,

I started a new thread regarding the Mikuni jet needle chart. Feel free to chime in with any info you want to share.

http://www.thegsresources.com/_forum/showthread.php?230879-How-to-read-the-Mikuni-jet-needle-chart&p=2169319#post2169319

[tirebiter]

A wideband o2 AFR gauge setup for $160 really saves a TON of tuning time

Oh YES !!! But where do you find one for $160.00 ? Have they come down THAT much ? Last I looked it was in the $350.00 range.

[Chuck78]

I posted in the product reviews. There are a few AEM and Innovate brand options under $200. Look for a post from last year in there by me on wideband's. Only difference I would look for now is maybe one that just had a small LED readout panel that I could incorporate permanently into an LED light indicator lamp panel so I could leave it on full time. There are a few companies that make those. Having one transferable to multiple bikes is very nice, however.

[tirebiter]

Found it. Thanks again Chuck78