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  Topic Review (Newest First)
07-30-2019 02:17 PM
7milesout
Quote:
Originally Posted by reb2005 View Post
7milesout -- waiting for your AFR graphs!

Unfortunately, there won't be any data acquisition. I wish there was a convenient way for me to get it done.


I have a GoPro and can video but I don't know how to edit the video, or record my voice during the course of the video.


I may video my runs and then can document the results from watching the video(s). But I'm also going to document 50 - 70 mph times, as well as top speed (no changes but jetting).


There's been some progress. See the "52 mm ARF gauge mounting" thread.




7milesout
07-30-2019 11:07 AM
reb2005 7milesout -- waiting for your AFR graphs!

Quote:
Originally Posted by 7milesout View Post
I'm anxious to get the AFR gauge on my rebel to see how accurate it holds the AFRs.
07-27-2019 12:58 PM
7milesout I'm not an expert but I've learned a lot playing with my Scamp, it's carburetor, and the AFR gauge. But I think the way our carbs work is the cable turns a throttle valve open to allow more air. But the slide doesn't move 1:1 with the throttle. The slide works on engine side vacuum. When the engine pulls more air through the vacuum increases and the slide begins to rise. The slide in turn controls the maximum amount of air the engine can draw past it while simultaneously contolling how much fuel goes to the engine because that slide acting on vacuum is also pulling the jet needle up out of the main jet and (needle jet?). The AFR stays more constant due to this design.

My Scamp's Edelbrock carb doesn't work this way. The throttle valve just slams open, air is going in and unless the carb set up is proper, it will go lean. And it is very difficult to get it proper. My Scamp is tuned to perfection though and it still has conditions where it goes too lean.

So I'm anxious to get the AFR gauge on my rebel to see how accurate it holds the AFRs.


7milesout
07-25-2019 05:16 PM
reb2005 OK now I see post #25.

In my defense, I didn't know what "CV slide" meant. So it must mean "Constant Velocity". I was wondering why they call these "constant velocity carburetors".

Quote:
Originally Posted by 7milesout View Post
The CV slide is sticky, and getting stuck not fully slid up. AFRs still good slide not all the way up, therefore the jet needle is not all the way up, AFR good, spark plug color good.
07-21-2019 04:47 PM
reb2005 The diaphragm was too shrunk to seal in the grooves. Temporarily yes, with the tape method, but one edge was not set properly and slipped after a few hours engine time.

I searched online for "wintergreen" and several say they have soaked the diaphragm in DOT 3 brake fluid without problems. A few warn that it could degrade the diaphragm.

So I used DOT 4 (similar to DOT 3) brake fluid and in 3 hours the diaphragm returned to original size, and seated perfectly. Engine now runs fine, knock-on-wood.

---

My choke nut threads are fatigued. Have to wire the nut down for security. I bought it used on eBay; been through three of these so far. I think all used choke nuts are fatigued. They don't strip like metal threads, they just lose their strength, and everyone "strips" them until they learn the deal. So... I think I should have bought a new one in the first place.

==================
Quote:
Originally Posted by flitecontrol View Post
Hmmm. Once the diaphragm lips are completely in the grooves, even if slightly shrunken, they should stay put. When you get it out, inspect the diaphragm for tears. IIRC, I ordered oil of wintergreen from a veterinary supply. Got like a quart for less than 4-8 ounces elsewhere. I now have a couple of lifetimes' supply!
07-20-2019 09:26 AM
flitecontrol
Quote:
Originally Posted by reb2005 View Post
My Rebel returned to its 50 mph top speed after a few hours of expressway cruising, as the diaphragm apparently slid out of its grooves
Hmmm. Once the diaphragm lips are completely in the grooves, even if slightly shrunken, they should stay put. When you get it out, inspect the diaphragm for tears. IIRC, I ordered oil of wintergreen from a veterinary supply. Got like a quart for less than 4-8 ounces elsewhere. I now have a couple of lifetimes' supply!
07-20-2019 09:18 AM
flitecontrol If you find one to fit the Rebel carb(s) for less than $70, let us know.
07-20-2019 08:42 AM
7milesout I wonder if a new diaphragm could be procured for not so much money...
07-20-2019 07:15 AM
reb2005 Here is a copy of Flightcontrol's

Quote:

Rejuvenating Rubber Parts:

Been hearing about using Wintergreen oil to soften old rubber parts and decided I'd try it. Had a first generation carb diaphragm that had shrunk a little and the lip wasn't seating in the groove it's supposed to mate with. At $70-100 just for the rubber replacement, it was a no-brainer. I mixed rubbing alcohol about 10:1 with Wintergreen oil, put the diaphragm in the mixture, and left it overnight. Took it out in the morning, rinsed with water and voila! The lip fit in the groove and the rubber was soft, pliable and minty. I've read where others have used it on old, stiff carb boots with similar results.

endQuote

I will be doing this ASAP: My Rebel returned to its 50 mph top speed after a few hours of expressway cruising, as the diaphragm apparently slid out of its grooves
07-20-2019 07:12 AM
reb2005 Your project sounds essential; looking forward to progress reports.

Nevertheless, to be conservative, I have heard stories (example: Kawasaki 750cc) having burnt valves when sitting in traffic on a hot day after exiting from an expressway.
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