I just posted to Hondaman (Mark) some jetting questions. I need to set my carbs up for an increase in altitude (89 ft. to 7000 ft.) As I'm going along to order other parts a lot of other questions are popping up. There is quite a bit of conflicting info as I go through the search function. I've been on this forum since 2005 and I have a good idea of who's who and would give the correct info.
To start, the bike is a 75 750K. It has 657B carbs. I need to order fuel tee o-rings. 1 guy says he got 2x8mm viton o rings in a 10 pack from Amazon. Another guy said the 2mm didn't look right so he got 1.8 mm. Does anyone know if the 2 mm will work? The next thing is fuel line. Most people are saying use 5.5 mm hose and it seals fine without clamps. Also they are specifying Tygon. Everything I'm seeing on 4 into 1 or Amazon is 1/4" or 3/16". Will I have to go to a specific place to get the metric stuff. I am going to have to redo all my lines because I'm going from a stock 75 tank with left side petcock to earlier right side petcock tank. The left side petcock has one outlet. The right side has 2. Does one hose go to #1&2 carb and the other to #3&4?
I just bought new insulators for the carbs. Also got new side covers from Frankenstuff . Got new speed nuts to install the new badges that I bought a few years back. I'm currently itching to get this bike back on the road. I took it apart back in 2014 to change cam pucks,engine paint,cover polishing, frame kit etc. Life,family health issues, a major move all got in the way. I just rode my son's Harley a couple of weeks ago so the urge to ride is back in a big way.
Anyhow, thanks for any info to help me out.
Yes, the 2x8 o-rings will fit just fine. The 1.9x7.9 that Honda lists is the MINIMUM size that will work. I use 2x8 in all the rebuilds, as they are far cheaper than the custom ones, and they will soften up over time when wet (and get hard when dry, totally normal). You don't need viton.
Honda sells the 5.5mm hose in an ethanol-resistant type: you'll know that by the dull red stripe running along on the hose.
Jetting: I live at 6000 feet and usually ride much higher, stock jetting, so long as you don't have #115 Keihin or #120 Keyster mainjets, will be fine. With the 657B carbs the floats are normally set slightly lean for those plastic floats, anyway. You can set them at 26mm instead of 25mm if your plugs tend to be too dark, otherwise I prefer the 25mm depth. Set the air screws to 3/4 to 7/8 turn for the proper idle mix, still within the air screw's adjustment range. Mine run right in between those 2 values.
The air hoses: all of those made today are between 1-2mm too small OD overall because the rubber is not as thick as the old ones. This means the clamps, especially the ones at the head side, won't seal very well. I recommend using the Oetiker clamps (at Aircraft Spruce) #050-9 at the head side. Just don't tighten them TOO tight, as they are aircraft-quality and able to cut clean thru the rubber (no, I won't tell you how I know that...).
