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Old 06-29-2011, 07:31 PM   #1
hypoman
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Default v45 magna excessive fuel? jet sizes etc please?

hi guys, im new to the forum and hope to bleed some good info from other fellow riders!

2 weeks ago i bought a v45 magna 750 (i think its an 83 model) here in the Philippines.
We went on a long run and its chewing up heaps of fuel. When you rev it up the exhausts blow black smoke and all 4 plugs are pretty black.

can someone please advise me of the correct jet sizes for this model? and what jets and needles are for the front or rear carbs?

2 of the slide diaphrams were incorrectly seated so were leaking air from a 2cm area. there wasnt any bad buildup of debris in the carbs and they were generally pretty clean.

being here in the philippines good mechanics are hard to find and i suspect someone else has incorrectly refitted the slide needles and maybe fitted oversized jets. (incidently the slide needles are non adjustable but in good condition).

any help greatly appreciated...
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Old 06-30-2011, 05:22 AM   #2
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2 of the slide diaphrams were incorrectly seated....
Since you seem to know a little about what you are doing.....

Is it safe to assume that you have checked the choke/enricher to be sure it isn't being run in the ON position ? and that the air filter isn't plugged up ??

Beyond that, I think you are on the right track with an inept previous owner screwing up the jets.
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Old 06-30-2011, 05:40 PM   #3
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thanks for the reply easyrider2,
mate the airfilter was ok, thats the first thing i checked. Im a little doubtful about the airbox though, I'm not sure if its delivering enough air to the filter due to the small opening. Ill look into that after i check the jets and reassemble the carbs later today.
I downloaded a copy of a workshop manual last night so have the specs i needed.
the choke is operating as it should be and not 'on'.

hows this, you know the 2 fuel line joint rails? they were broken so i superglued one back together as a sample and took them to a local machine shop. they turned them up for me out of steel and braised the fuel inlet pipe to them, they even turned up a barbed end on the input pipe. all for 600 pesos (about $15 US) for the pair.
gotta love that!
cheers...
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Old 07-01-2011, 06:53 AM   #4
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Im a little doubtful about the airbox though, I'm not sure if its delivering enough air to the filter due to the small opening.
If the air box is stock, you shouldn't have to worry about the opening being big enough........unless you have a rag stuck in it. (Wonder why I would mention that ???)

That theory is easy enough to test though. Take the filter out and leave the airbox open long enough for a short test ride.......not on a dirt road though.
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Old 07-01-2011, 10:50 AM   #5
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If the air box is stock, you shouldn't have to worry about the opening being big enough........unless you have a rag stuck in it. (Wonder why I would mention that ???)

That theory is easy enough to test though. Take the filter out and leave the airbox open long enough for a short test ride.......not on a dirt road though.
The thing is, if someone has put substantially-larger jets in the thing, it might run BETTER without the filter and airbox-top.

If it's "stock", it might not run at all without the airbox cover.
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Old 07-02-2011, 07:11 AM   #6
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The thing is, if someone has put substantially-larger jets in the thing, it might run BETTER without the filter and airbox-top.

If it's "stock", it might not run at all without the airbox cover.
Yes and yes.

Thus the short test to see which applys in HIS situation.
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