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Well thanks for the insights. Will have to give her a go in about 5 months when the snow disappears.
One thing that i haven't done yet is check my plugs and should have done this before i started the post. I don't have a heated shop and the wife won't allow me to bring the bike into the house. Will have to wait untill it warms up a bit.
 The plugs will tell the tale. Just before winter hit us I had a chance to take it on a 3hr highway cruise and run it 3/4 throttle or more for most of the trip.
 Black plugs means too large a jet , white plugs means too small of a jet. I like to err on the richer side myself. Too lean is asking for trouble.
I have had a fair bit of experience with carbs and know that my a/f is good and my mid range is good. Was just curious as to what size mains other 800's where running. Takes me awhile to get mail order up here in the sticks and thought that I would order a few sizes ahead of time.
 I am not a fan of radical modifications so my bike is only slightly modded. I may have to accept that without major mods this is what i have to live with.
 My set up is.......... K&N air filter, marbled, partially modified air box, partially de-baffled OEM exhaust,  Dyno-jet  carb kit installed,new plugs, valve clearance checked, running seafoam in premium fuel, Had 18/38 sprocket but went back to 17/40 to get more torque in 5th gear.
 My 5th is running about 4500 - 5000 rpms around the 75mph range. She just can't sustain that on a big hill or in a strong head wind. Shifting down is the only option but don't want to run 6000 rpms in 4th to hold the speed.
 My biggest issue i think is the windshield. It was large to start with and then i added lowers and some small extensions.  I've got the equivalent of half a sheet of plywood up front holding me back.
R

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Posted by Lucky

- December 17, 2019, 06:51:12 AM

First and foremost
dynaojet sizes are LARGER than everyone else's sizes
https://www.jetsrus.com/FAQs/FAQ_mikuni_vs_dynojet_vs_keihin_sizes.htm

a dj136 is everyone else's 140

secondly, the main is only important past 1/2 OPEN, not necessarily RPM or speed, but the actual lift of the slider. unless you are in high RPMs, which is the normal buttdyno way to test performance, a larger main isn't going to help you .. that is, if you are cruising in 5th and have to romp the throttle to get up a hill, and the engine doesn't REV!!!!, you should just down shift, as a larger main won't do anything for this circumstance

so, here's a test -- and it's backwards from what you are asking, but try it anyway --

find a hill that is fairly close by and offers a challenge.. go hit it 2-3 times, just as normal, helps if you have a stop watch and get a feel for it.. decide what gear and what speed you hit this in, and stick to it.

then remove your airfilter and repeat -- this is actually LEANING the bike by allowing more airflow

is there a noticeable difference, other than the really cool sound of air rushing in? i bet there is zero to "its faster with the aircleaner off"

then, put the AC back on, and down shift before the hill .. i tend to baby my bike, so this was a little strange for me -- but going from 3800 rpm to 4600 isn't going to hurt her (i use a cheapo $9 tach ziptied to my bars) and see if she goes up the hill better.

just for reference, i am (now) 225# 6'4, and yes, she climbs better now that i've lost 50#

changing the main larger without MAJOR changes to the exhaust and air system isn't going to yield much, except she'll run a little cooler

have you adjusted your A/F mixture screw? what tooth sprockets ?

Posted by rob f

- December 16, 2019, 17:20:11 PM

I am still struggling with getting a bit more power out of my 800 and am looking at changing the main jet. Right now I am running a DJ136 which was the biggest jet in the dyno jet kit that i installed. The bike seems to be running nice through all the ranges but uphill and against the wind the throttle is wicked right out. I see that in some posts that guys say that they are running a 155 main jet. Now is that a DJ number or a Keihin number? A DJ 155 tranlates over to a Keinin 170. My OEM jet was a 135.
Anybody know what main jet you have in your bike?
Rob

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