Miles to the gallon?

Miles to the gallon?

Postby bic_bicknell » Fri May 30, 2014 2:54 pm

I've still got problems with engine on my newly acquired H2C, I think it's going to have to wait for the new CDI unit to come from the States. But the intermittent problem has not stopped me going out and when it runs on all three cylinders crisply it seems fine. It's just hit or miss at the moment.

I've just finished another tank of petrol and have done enough miles to do a first calculation of this bike's thirst for fuel.

Basically it's doing 3.4 miles to the litre or 15.4 miles to the gallon :o I know these bikes were meant to be bad but this is shocking. Is this normal? Whenever I chop the plugs they always seems to be black and wet, not yet seen a dry plug and certainly not a light brown one.

I am beginning to suspect that this bike hasn't ever been set up properly. Maybe it's just running massively rich?

It would be good to get someone who knows triples well to have a thorough look at the ignition and fuelling. Is there anyone you guys could recommend in the South London/Surrey/West Sussex area?
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Re: Miles to the gallon?

Postby Jim » Fri May 30, 2014 3:31 pm

I get around 30 miles per US gallon with my H2. RB gets like 127 mpg. Guys who jet on the rich side get numbers in the 20s. If you're intermittently losing a cylinder, that might explain very low numbers. I'm working on the CDI units...
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Re: Miles to the gallon?

Postby Wolfie » Fri May 30, 2014 4:53 pm

What size sprockets have you got Bic?

If you have 14t at the front then that's just pretty thirsty... if you have a 16t then that might indicate a problem including the one as above. People regularly get 40+ on 16t sprockets (but can sometimes make it down into the teens when really trying hard).
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Re: Miles to the gallon?

Postby bic_bicknell » Fri May 30, 2014 8:14 pm

I'll check the sprocket tooth count tomorrow. What's the original factory sprocket size front and rear?

I find this bike fascinating to ride as I get used to it. Just like my Superduke, it doesn't really feel happy pootling around. It wants to go fast.

So having to get used to riding a 2 stroke again :D It's like 30 years have not happened, I shift back into two stroke mode quite easily, feels like home, but this 750 is still four-stroking all the time at most legal road speeds and then if you shift down a gear it's revving and vibrating but just wants to accelerate. It's hard to hold it on a throttle position that feels right. But then when you get on open roads with no traffic it all makes more sense because you don't cruise along at a constant speed. This bike seems so much better when you are just accelerating flat out to the red line and then braking,(as best you can), then flat out again. Seems to be what it likes and makes for a better ride. I wouldn't want to do a lot of long distance, steady cruising on this bike!!

Brakes are getting better, I really think that the pads were not bedded in. Hopefully things will get better still. I've done about 200-250 miles so far. I can now make the front tyre squeal at 30mph with a really hard fistful so it does make me realise that upgrading the brakes will only be as good as these skinny tyres and dubious compounds. As better braking come in I can start to get a measure of the front fork and damping. Modern bikes are so forgiving if you brake into bends. This one likes to do it's braking upright and there are some interesting things that happen if you experiment with brakes and lean angle!

So far I love the handling. I'm not comparing it to a modern bike, just my impressions of the feel across a mixture of A, B roads and roundabouts. It's pretty planted and stable. Bumpy back roads do set it off into a series of bounces but that's only when you're going fast and I've had no really scary moments yet.

Anyway, still grinning! :lol:
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Re: Miles to the gallon?

Postby RB » Fri May 30, 2014 8:55 pm

Jim wrote: RB gets like 127 mpg. Guys who jet on the rich side get numbers in the 20s. ...

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That isn't as ridiculous as it sounds :shock: If someone is up for a bet, then I probably could get that figure with stock everything . . . it would be a S L O W ride . . .but I'd take the bet :think
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For anyone else, a basic rule of thumb, 18 - 26 around town, general riding 32 and 40 ish on a run (not exceeding 80 MPH) ;)
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Re: Miles to the gallon?

Postby Wolfie » Fri May 30, 2014 9:37 pm

I think 15t was the factory fit.

14t for fun and 16t for economy and motorway.
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Re: Miles to the gallon?

Postby ja-moo » Sat May 31, 2014 1:27 am

15 was fitted in the US, and according to the manual 16 in Europe....... :wave
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Re: Miles to the gallon?

Postby bic_bicknell » Sat May 31, 2014 8:37 am

It's got a 15 on it.
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Re: Miles to the gallon?

Postby Scouse » Sat May 31, 2014 5:33 pm

45 mpg, but mine has 34's, expansions and reprofiled heads for modern fuel

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Last edited by Scouse on Sun Jun 01, 2014 3:48 am, edited 4 times in total.
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Re: Miles to the gallon?

Postby ja-moo » Sat May 31, 2014 7:42 pm

You have to do a few upgrades on a 74/75 to actually get it to handle nicely. But yours is too "stock" to do them.
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