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Thread: re-jetting carbs
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10-21-2016, 02:49 PM #1
re-jetting carbs
When you carb gurus have to increase the jetting on your carbs where do you start, up 2-sizes? Up 4 sizes? I got my new engine (99 2.5 200) together and broken in with some WH-22's and I want to put the WMV-18's back on. They seem to have had better throttle response, idled smoother and got better MPG than the WH-22's. When I got the WH-22's I was told by James Perry what jetting he has had the best success with and everything seemed fine. Another well known builder on here suggested I try some WMV-18's as they were a newer carb with better technology and he had experienced much better success performance wise as well as fuel mileage.
My new engine is .015 over and on the tight side of tolerance as I don't spin the RPM you hardcore guys do and I need it to last (at least until I get that XB2002 my heart desires), steel cage bearings, rod slots were done, exhaust chest opened up, exhaust ports touched up and heavy chamfered, 1" Chris Carson spacer and reeds, short bell-mouth tuner, 33cc heads (have a set of 28cc for just in case ) and I have opened up my cowling in the front to allow more air in.
So, suggestions as to how much I should increase these jets to start with? I have EGT probes and a gauge in the dash so I can TRY to not melt this thing down.
SlimmLast edited by Slimm; 10-21-2016 at 03:11 PM. Reason: spelling
Hire the handicapped, we're fun to watch
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10-21-2016, 08:27 PM #2
I usually go up 4 sizes which Is .008 larger than stock then adjust from there. Every motor/boat/set up combination is different.
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10-21-2016, 08:31 PM #3
With the motor being tight I recommend running a little on rich side to help keep piston cool. It'll live a lot longer and you'll have that cushion if something goes wrong or get bad fuel and such.
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Slimm liked this post
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10-21-2016, 08:44 PM #4
Sorry I forgot to mention that I have about 15 1/2 hours on it since rebuild. I for sure want to keep it on the fat side. Thanks for the input, that gives me a place to start.
SlimmHire the handicapped, we're fun to watch
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10-21-2016, 08:49 PM #5
Your welcome. First time out I always like to take it easy and shut engine at cruising speed and inspect plugs/pistons to make sure definantly have enough fuel then slowly work your way up. That is if boat will allow you to that without much backwash.
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10-25-2016, 10:46 PM #6
WMV's ran the best on mine....the WH series carb did not impress me one bit.
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11-02-2016, 10:06 PM #7
It is way easier to and cheaper to change jets than pistons!
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Slimm liked this post
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11-16-2016, 11:41 PM #8
I use the WH series a lot because they are plentiful and because they don't have the progressive jets they run lean (not enough to hurt the engine) in the mid range and get better economy which is a good point for most people but can be made to run very well if you jet them correctly. I gave you a base to start with as each engine is different due to difference in load, baro, ect. Just my .02
James Perry
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