Author Topic: 750 Hondamatic tuning (Read 4912 times)

Chuck Hahn · « **on:** September 17, 2012, 04:42:04 PM »

Got a few days off and tackled the valve adjustment. Triple checked everything according to the service manual and am sure they are all done right. So..took it for a ride down to a buddies place about 70 miles away. Filled it up and ran the interstate at an average of 75 MPH. Stopped and filled it up to the same level as when i left and it took 3.1 gallons. Thats an average of around 23 to 24 MPG. Sinmce this is my first Hondamatic, I was wondering if this is good for the bikesize and travel speed or not. I was thinking it should be around 32 to 35 average?

?

77Pinto · « **Reply #1 on:** September 23, 2012, 04:51:34 PM »

With minimal highway use, mine will get 35 MPG no problem. I have done some highway and even without checking it I can tell its much less. My 76 Wing was the same way, once you get to a point it just DROPS off.

Bill

JimS63 · « **Reply #2 on:** September 23, 2012, 05:24:49 PM »

I haven't done much freeway riding yet, but mine gets about 35-38mpg on city/backroads riding 35-50mph roads (and I'm not babying it).

salukispeed · « **Reply #3 on:** September 24, 2012, 09:29:48 AM »

MY 77 auto regurlarly gets 40+ with a mix of highway but limited to 60 and 65 mph and 50-55 on rural back roads. I have seen 51mpg on a full tank but would ever not count on that. after 70mph mileage seems to drop to around 40. I drive fairly conservitively most of the time.

Chuck Hahn · « **Reply #4 on:** September 27, 2012, 01:20:42 PM »

I have done the 24 HR soak in Berrymans, new orings on everything, tc etc etc. I think it should be above 24ish even at the speed I posted. So basically mine is getting about 2/3 of what it should be getting. Valves have been adjusted too by the way and are all within specs according to the factory service manual I have. Any ideas as to what to be checking to maybe up the fuel economy?

05c50 · « **Reply #5 on:** September 27, 2012, 08:28:36 PM »

How does it perform? Have you checked the spark plugs? Do that look black and sooty? How about the points? Timing might be retarded or maybe the advancer isn't working properly. Other things that cause poor fuel economy: fuel leak (obvious??), brakes dragging, park brake not releasing completely. Mine gets about 30 to 35 mpg, but I never ride 75mph.

...........Paul

Sam Green Racing · « **Reply #6 on:** September 28, 2012, 02:46:10 AM »

You would worry about fuel consumption if you had to pay UK prices.

Chuck Hahn · « **Reply #7 on:** September 28, 2012, 07:45:05 AM »

05c50..she runs fine and has plenty of get up and go. I have noticed that it fires right up from being dead cold without any choke at all....not like my old suzukis that require a bit of help from the enrichment circuit. Also the idle seems a but high till it warms up and then it settles down. I havent done anything to the bike after i got it other than the carb rebuild and the valve adjustment. It was a running bike when i got it. How far out do the fuel screws get set..maybe i have them set wrong also.

salukispeed · « **Reply #8 on:** September 28, 2012, 09:22:31 AM »

What are your float levels set to. Hows the air cleaner? I did not notice if you synchronized the carbs after the cleaning. Have you checked the points and the timing with a strobe/timing light. Mine had the advancer siezed and never advanced properly. Only found it with a light. I believe most of the folks here shoot for mixture screws set to get the highest idle when hot. Wear some light gloves as it is painfull to get to the 2-3 mixture screws when fully warmed up. I am always complaining about fuel prices here and you have it much worse.

Chuck Hahn · « **Reply #9 on:** September 29, 2012, 07:41:13 AM »

I did do the sync with my guages. I was told to just hook the 4 adapters directly to the intake boots, but the service manual mentioned something about using the vacuum adapter tool...maybe i did that wrong??? How should I have hooked the guages to the bike correctly? I assume by adapter tool, they mean that it goes in the vacuum hose that tees off to the accellerator module thing.

salukispeed · « **Reply #10 on:** September 29, 2012, 09:31:16 AM »

You are only looking to get a nice solid connection to each of the intake ports so each gage gets a reading of the vacuum in that port. I adapted one of my hoses to fit on the nipple that the tube to the speed up solenoid is connected to and used my adaptors on the remaining three. You can only adjust three of the four carbs and match it to the unadjustable one. I forget if it is #2 or #3. the closer the better and definately under 1 inch varation. . If you can stand the heat it is then a good time to tweak the mixture screws and get the highest reading out of each. Mine ended up around 1 1/2 to 2 turns out but yours may differ. Its kind of a game of round robin- set speed- set mixture-speed-mixture until your there. Using a strong fan blowing on the front of the engine can help keep the exhaust from turning colors and temps down.

05c50 · « **Reply #11 on:** September 29, 2012, 09:48:50 AM »

I'm not sure what you did, but let me describe the connections and you can take it from there. Towards the top and front of each carb is a small screw that screws into the throat of the carb. remove the screw and screw in the vacuum adapter, then connect one gauge to each adapter. The idea is to adjust the carb so that the vacuum reading on all gauges is as close as possible. The adjustment is NOT made with the mixture screws, but with the adjustments under the caps on top of the carbs. Hope this helps.

.........Paul

Chuck Hahn · « **Reply #12 on:** September 29, 2012, 09:51:59 AM »

The part thats confusing me is at that palstic tee for the selinoid...the guy told me to just screw in all 4 adapeter straight to the ports and that the bike doesnt need the selinoid to do the carb sync. So to clarify, do i need to have the selinoid in curcuit while doing the sync or not? If so, i suppose that i can get a plastic tee at the auto parts to make an inline adapter so I can run 1 leg to the guages and another to the selinoid...this make sense??

Chuck Hahn · « **Reply #13 on:** September 29, 2012, 09:55:21 AM »

Paul...yes that what i did..just the same way i do the VM carbs on the GS Suzukis i have. Loosen the jam nut and adjusted each set screw till all the guages were the same across the board. I did not have the selinoid in use when I did the sync...adapters straight to the ports and each hose directly to the guages from each adapter.

05c50 · « **Reply #14 on:** September 29, 2012, 12:43:07 PM »

Yep, sounds like you did it right. The solenoid doesn't need to be involved in the procedure. The solenoid effects all carbs equally. Have you looked at the color of the spark plugs?

........Paul

Chuck Hahn · « **Reply #15 on:** September 30, 2012, 08:41:10 AM »

I am thinking that reverification of the float heights and reapplication of the guages will be a few good starting points.

JimS63 · « **Reply #16 on:** October 03, 2012, 08:11:56 PM »

I filled up today and did the math. I got 38.2 mpg. That's commute riding....city and backroads. And I'm a big guy.....

Chuck Hahn · « **Reply #17 on:** October 03, 2012, 08:32:02 PM »

At what as an overall average speed???

JimS63 · « **Reply #18 on:** October 04, 2012, 08:26:07 AM »

Mostly city and backroad riding. 35-50mph stuff. I'm only on the freeway for about a mile at 65 (I try and avoid the freeways).

SGTBob · « **Reply #19 on:** October 14, 2012, 01:15:22 PM »

For my last ride of the season, I rode the bike until it was at least 3/4 empty. Riding at typical 55-60 mph I averaged 36 mpg. Almost without fail, every time I ridden and filled after the ride, my mileage has been consistantly 35-38.

I have only had it on the highway (I-94) for about 7-9 miles and I did not like riding it at the speeds necessary to keep from getting run over

(75+ mph), so I can't speak for "highway miles".

Chuck Hahn · « **Reply #20 on:** October 16, 2012, 11:09:48 PM »

I dig highway speeds...the bike is smooth and a joy at 75 and 80 MPH. Im ride a lot to Austin, which is about 75 miles from my house and thats on I35. Thats where I had done some filling up going and coming back and found that i was averaging pretty low as to what i had imagined it would be...thus my inquiry here.

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Author Topic: 750 Hondamatic tuning (Read 4912 times)