Author Topic: 77 convert  (Read 1828 times)

Offline moto

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Re: 77 convert
« Reply #60 on: July 20, 2021, 06:00:54 PM »
You can time the flow with a measuring cup to see if it is sufficient. For example, to go 70 mph at 35 mpg would take 2 gallons per hour. That's 32 cups of gasoline per hour, or a rate of 1 cup every one-thirtysecondth of an hour. Using 1 thirtieth as an approximation, that's about 2 minutes to fill an 8-ounce cup. If both petcocks together can't do that you may have a problem.

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Offline twodogs

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Re: 77 convert
« Reply #61 on: July 21, 2021, 08:45:02 AM »
1st round, I pulled the right side while sitting on the bike fuel line and measured about 6 ounces in 15 seconds with a stop watch then went to the left side and measured a hair over 5 ounces in 15 seconds, there was no water or debris in the gas that I could see after letting each time sit for about 3 minutes, so I'm not sure if the petcock screens have debris on them, seemed to me to flow pretty good to me, what do you folks think? I think I'm going to take it out and see if I can replicate the problem and then do the flow test again if it acts up again, I've run the bike for 220 miles so far with only the last 30 with the problem of not being able to get fuel, that feeling anyway, plus when I take it out again and burn more fuel off it will help if I have to remove the tank, who thought that about 6 gallons in a tank could weigh so much  :rolleyes:
Bruce
2019 Suzuki Burgma
2021 Zero SR
1977 MG Convert

Offline moto

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Re: 77 convert
« Reply #62 on: July 21, 2021, 09:59:42 AM »
1st round, I pulled the right side while sitting on the bike fuel line and measured about 6 ounces in 15 seconds with a stop watch then went to the left side and measured a hair over 5 ounces in 15 seconds, there was no water or debris in the gas that I could see after letting each time sit for about 3 minutes, so I'm not sure if the petcock screens have debris on them, seemed to me to flow pretty good to me, what do you folks think? I think I'm going to take it out and see if I can replicate the problem and then do the flow test again if it acts up again, I've run the bike for 220 miles so far with only the last 30 with the problem of not being able to get fuel, that feeling anyway, plus when I take it out again and burn more fuel off it will help if I have to remove the tank, who thought that about 6 gallons in a tank could weigh so much  :rolleyes:
Bruce

The rate I calculated was 2 gallons per hour, to support a (dismal) 35 mpg at 70 mph. Since there are 128 ounces in a gallon, that rate is 256 ounces per hour, or 4.27 ounces per minute, or 1.07 ounces per 15 seconds. So your flow at the petcock is five or six times as great (on each side) as your actual total requirement at that speed. It is also more than enough to support 100 mph at any reasonable mpg figure.

But what about the flow rate after the fuel leaves the petcock? For that, just take off the drain plugs at the bottom of each carburetor in turn, and turn on the petcocks without trying to start the engine. If you again see flow rates of multiple ounces per 15 seconds through each carb, then your problem isn't fuel flow. On the other hand, if you get down near or below 1 ounce per 15 seconds in either carb you can suspect a clogged filter or float valve or other obstruction in the flow below the petcock.

It is barely possible that you could have a flow problem that only manifests itself when both carburetors are demanding fuel. To check for that, open both the drain plugs at once and measure the combined flow. Anything above 1 ounce per 15 seconds in total supports 70 mph at 35 mpg, but you should really see substantially more than that for higher speeds.

Moto
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Italjet Buccaneer 250 (ex-SSR)
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Offline twodogs

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Re: 77 convert
« Reply #63 on: July 21, 2021, 11:25:24 AM »
Thanks for the reply moto, I could not get to the left side because of the stock air box so I did both sides after the fuel filters I put on and I was thinking that they were the problem, anyway I forgot to mention I put sea foam in it yesterday, so I took off this morning just to see if those filters were the problem and I got about 1 mile out of town and it would not go so I turned around to nurse it back home and it started picking up, so I turned back around and gave her hell in 1st and it run like a scalded dog (vert) style anyway, so after about 15 miles of that I stopped and put it in 2nd and rode for another 55 miles at 70 and then backing off and charging back up to 70 and it never missed a beat and then the speedometer cable broke, so I got a cable coming and I will try it again,plus I need to tighten the neck bearings up a little, gets a little weird above 70. I always thought seafoam was all between the ears but maybe it knocked some crap loose and just took it awhile to work, don't know for sure but after I take care of the neck bearings and speedo cable I'll take her back out and try it again. Thanks for the help folks.
Bruce
2019 Suzuki Burgma
2021 Zero SR
1977 MG Convert

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Re: 77 convert
« Reply #63 on: July 21, 2021, 11:25:24 AM »

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