Ninja EX500 carbs on an XS650?

I was told, (by you), i was on your ignore list...............keep it that way will you.

You are trolling.......No need to comment on my comments that aren't directed at you ....or at all

thats rich coming from the sites main Troll ! Anyone bothering to check any of my past posts will soon see who is the troll that constantly criticises practically every post I make over the past 5 years.

I'm not going to let you drive this thread into the ground with your petty arguments and vindictive vitriol so I'm going to leave it to you to advise the PO how he should sort his carburation issue. Oh I forgot you don't know anything about carb troubleshooting and setting up do you
 
Right, been out for a few runs with my new 1.5" stainless pipes, and I reckon I might be a tad lean on the mains; I could maintain a steady (albeit buzzy) 90mph with the standard pipes, but now I get to 80mph and it runs out of puff.

I went with 38/138 and JJJ(middle clip). Here are my plugs, a bit white??
View attachment 128762

View attachment 128763
I have some 142 jets ready to go, might be a big jump from 138? I noticed someone else with foam pods/straight through exhaust had 140s.

Thanks carb gurus

Highboy
a useful test for testing main jetting on the road is to open the throttles up to full throttle in 4th or 5th gear............ then when the engine seems to plateau or run out of steam... back the throttle off very slightly ........about 1/8th .......... Note what happens .

Try it a few times until its clear whether the engine seems to hesitate (rich mixture ) or it seems to pick up slightly as the throttle is backed off 1/8th .
If the engine picks up the mixture is likely too lean and you will need to go up on your main jets .

if the engine hesitates or shows no response then its likely your main jets are either too rich or they actually may be close to optimum ,(check plugs after long test ride at 3/4 to WOT )in which case you'll need to look elsewhere for the power drop ie exhaust...
 
Highboy, if you roll off slightly from WOT and the bike pulls better and harder, that's usually a sign your main is too big, not too small like peanut said.
 
Yes, you seem very close. You're probably no more than one little tweak or jet size change away.
 
Highboy, if you roll off slightly from WOT and the bike pulls better and harder, that's usually a sign your main is too big, not too small like peanut said.

You seem to be contradicting yourself 5T . This is an excerpt from your 'carb guide' in which you state

'under full throttle applications. If the bike pulls clean through this RPM range with no flat spots (lean) or no stumbling or break-up (rich), go up a main jet size. If you do encounter a giant flat spot where the bike just kinda dies, then takes off, that's lean

to be fair there seems to be varying opinions about this if one surfs the net
but it really does not matter either way.

My suggestion of testing the throttle response at WOT by rolling off the throttle slightly and noting the response is a standard test and all that matters is the result .

If Highboy trys the 142 mains that he has there will be a difference in performance and that difference will tell him which way he needs to go with his main jets . Richer or weaker.

personally i don't believe that the main jets are the only issue here anyway.
Everyone seems to be overlooking the fact that the engine was apparently performing fine before the exhaust change !.......;)
Exhaust tuning is a complex subject and we have no real details about the replacement exhaust other than its bore size. Here is where a dyno session would prove valuable to see where the power curve lies comparing the 2x exhausts
 
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Its not my opinion its recommended practice to start over-rich and work down to correct jet size on main jets when testing at WOT.

I'm 'all for' the application of commonsense in the absence of available recommended good practice .
By the way what has adjusting idle mixture screws got to do with changing Main jets and WOT testing?

Peanut statements in red in his 5twins quote.
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1 dram to many LOL
 
Yes, I know he said that, but you can't tell this guy nuthin' ...... He pretty much forgets what he wrote in 20 minutes, lol. And his quote from the carb guide is incomplete and out of context. I'm pretty sure it's part of the midrange to main transition tests, not the main jet test.
 
yes i see the difference in the references.......Shame he doesn't read things properly himself instead of blaming others for doing the same thing.......

It feels a bit churlish posting his quotes to counter his claims. ..............................He actually gets people to listen to him through his browbeating of others who post contrary information to his...........makes out hes an injured party when other posts are different, because other opinions/information/facts are not the same as his.............. I removed my input after i bought a set of these carbs due to his argumentative behavior..........he changed a previous post so that information i posted after him was made to look like he had posted it first and then proceeded to berated me...........
 
Ok..
Just to clarify, you can see the exhaust here:
IMG-20181010-WA0001.jpg
It's a 1.5" 2 into 2 system, no crossover. There's perforated steel mesh inners in the mufflers but they are straight through, like many aftermarket systems, and an extra drag pipe baffle is then held in each one by a bolt.

Everything was pretty much perfect before the exhaist, and it ain't too bad now! Just that slight difference in top end. I considered the CVKs perfectly dialled in with 38/138 and the jjj needle. So the exhaust is the only factor here, and it is probably less restrictive than the standard pipes.
In line with what most people have said, yes it probably wants a bigger main; midrange is still great, idle is good, it never splutters or bogs down on snapping the throttle opens.
By comparison, snapping the throttle on the BS34s would nearly almost stall it, midrange was lumpy, but top end was fine.

Cheers for every other news help, I certainly didn't want to start any arguments!
 
Main Jet Testing using the 'Roll Off' method as recommended by the Mikuni American Corporation in their carburettors Tuning Guide.

http://www.mikuni.com/fs-tuning_guide.html
quote '
1: Main Jet Size: How to Get it Right
ROLL-OFF:


The Roll-Off technique is the quickest and is almost as accurate as the Roll-On method. First, one gets the engine warm on the way to a safe roadway. If there is room, use fourth gear as this allows more time to assess the result.

Now, get the engine rpm high enough that it is on the cam and in its power band. This may need to be as high as 4000 rpm with some cam choices. Apply full throttle. Let the engine accelerate for a couple of seconds until it has settled in and is pulling hard. Quickly roll the throttle off to about the 7/8ths position. When you do this, the mixture richens slightly for a second or so.

If the engine gains power as you roll the throttle off, then the main jet is too small
(ie too lean) and you need to fit a larger one.
If the engine staggers slightly or has a hard hesitation, then the main jet is too large ( ie too rich) and you need to fit a smaller one.
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Copyright (C) 2002, Mikuni American Corporation All Right Reserved.

5Twins post #907
Highboy, if you roll off slightly from WOT and the bike pulls better and harder, that's usually a sign your main is too big, not too small like peanut said.

Looks like you have your lean and rich mixed up :) but regardless ...what matters is ones personal experience and my experience is that when you roll of the throttle 1/8th at WOT in a high gear if the engine shows signs of picking up then the mixture is too lean and the Main jet needs increasing is size NOT decreasing in size
 
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Ok, little update, rolling off full throttle gives a slight burst of power, so that is just confirming the lean hypothesis! Now to try again with the bigger jet...
 
It will be interesting to see the result of using the 142 Mains.'
What have you got your re-jetting mains turnaround time down to now I wonder ?;)

I hope you haven't been doing 90mph in todays winds lol :eek:
 
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