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Old 08-08-2008, 02:03 PM   #1
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carb jets

hi
could anyone advise me on jet size mariner 150 40 thou over size pistons i am running std jets at the moment could i go up a size
any info please

regards

scott
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Old 09-08-2008, 07:47 PM   #2
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Scott
What is the reason you want to go bigger with the jets?

karl
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Old 09-08-2008, 08:24 PM   #3
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re jets

just wondering whether i could go up a size on the jets that's all just some advice
ie 200 jets or would i over fuel
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Old 09-08-2008, 08:46 PM   #4
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2 Strokes produce maximum power when the ratio is at it's weakest and just short of melting the pistons. So if the engine is running fine now an not close to the point of damaging the piston tops, any increase in fuel will reduce power if anything. That's why I asked for the reason.
Also the jets are matched to the venturi size of the carb more than they are to the size of the engine. So you can't relate jet sizes to a bigger engine without knowing the size of the carbs it's running.
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Old 09-08-2008, 09:41 PM   #5
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Quote:
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2 Strokes produce maximum power when the ratio is at it's weakest and just short of melting the pistons. So if the engine is running fine now an not close to the point of damaging the piston tops, any increase in fuel will reduce power if anything. That's why I asked for the reason.
Also the jets are matched to the venturi size of the carb more than they are to the size of the engine. So you can't relate jet sizes to a bigger engine without knowing the size of the carbs it's running.
thanks for the info its running std carbs but i have a set of xr2 carbs to go on my motor do you think these carbs will work?
any advice welcome

regards

scott
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Old 09-08-2008, 09:56 PM   #6
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they will need re jetting for your motor, this isn't an easy job unless you got an egt gauge and loads of different sized jets
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Old 09-08-2008, 10:03 PM   #7
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If you want easy power gains i'd get the heads skimmed to about 27cc which should give you about 150 psi of compression. go up a couple of jet sizes on your present carbs and away you go. Alternatively buy yourself an egt gauge Bad Boy has one for sale, wire it in and keep changing jet sizes till you achieve approx 1150 degrees at full throttle, this will be your optium fueling and safe power without going bang.
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Old 09-08-2008, 10:19 PM   #8
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cheers for the info
burty why arnt you in hunstanton then?
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Old 09-08-2008, 10:45 PM   #9
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going in the morning, supposed to be taking the kids to the balloon fiesta tonight but it was cancelled cus of the rain
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Old 09-08-2008, 10:56 PM   #10
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going in the morning, supposed to be taking the kids to the balloon fiesta tonight but it was cancelled cus of the rain
one hell of a drive in the morning then race and drive home sod that
good luck tomorrow
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Old 11-08-2008, 06:13 PM   #11
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Burty;

Wos a "egt" gauge?
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Old 11-08-2008, 06:49 PM   #12
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one hell of a drive in the morning then race and drive home sod that
good luck tomorrow

one heck of drive up, then NOT race then a long drive back
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Old 11-08-2008, 08:38 PM   #13
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Burty;

Wos a "egt" gauge?
Exhaust Gas Temperature
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Old 11-08-2008, 08:55 PM   #14
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Exhaust Gas Temperature
Cheers Burty ,,,,, & the cost?
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Old 11-08-2008, 09:42 PM   #15
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dunno dude, have a look at digitron in the US or rex marine
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Old 05-01-2009, 02:02 PM   #16
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Egt

FW Murphy do a exhaust pyrometer kit. Single or dual read out. You'll need a dual sytem for 'v's. The full dual kit which comprises of the following 1, Gauge. 2, 2xthermocouples. 3, 2xstandard leads (14ft in length) is £196. They have them on the shelf. Also you can buy an alarm switch to work with them, They are set to switch at 1100 but you can have them altered to your spec.

I've just ordered mine, I'll tell you in a few days what I think.
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Old 05-01-2009, 03:15 PM   #17
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Egt

Just been on ebay and there are quite a few to choose from, starting from £70. Not too sure how hardy they're going to be though. They look a little 'Halfords' like!!
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