SV650SX New Air Filter = Flat spot

Morning all

You may have read my other thread on improving MPG as mine was abysmal.

I believe may carbs have had the slides drilled and dynojetted, I have a new set of bog standard carbs on the way thanks to a .org member. In the mean time I have replaced the K&N had with a standard Air Filter, now the bike vibrates less and seems to idle better and is smoother through the revs except between 3500-4000rpm where there seems to be a flat spot, it will eventually pull through it but it seems to be in all gears.

Would the modified carbs have been set up to work with the K&N rather than a Std filter, I'm thinking this may be the cause of the flat spot.

Any advice opinions would be appreciated.

[yorkie_chris]

It may quite possibly have been rejetted.

I'd stick the stock carbs on and see what difference it makes.

Wow that was quick, the previous owner did say it had been jetted with the K&N and tracked for a while, I suspect it is highly likely.

I will whack the stock carbs in see what difference it makes.

Right the plot thickens, with the supposedly DJ'd carbs and standard filter my MPG has dropped from and average of 41mpg to 37mpg, I really hope the standard carbs help

It was up at 41mpg with the DJ's carbs and a K&N filter.

[johnnyrod]

Sounds like it's runnign badly rich

Would the new air filter have caused this, hopefully will be putting new carbs on the weekend.

It was running fine before on the K&N

Btw Idle is smooth and adjusted correctly

I have been reading up and I think that it is running rich due to the over-sized Dyno-Jet jet in there with the standard filter.

Hopefully standard carbs should sort it.

[johnnyrod]

It sounds like it's been upjetted too much, the K&N would flow more air so mitigate the problem a little compared to the stock filter (but your miserable mpg says it's probably been jetted beyond that point too). Standard carbs and filter will be a righteous combo. The noisy can will make it run leaner but probably still close enough to blat about on. Make sure the chokes on the new carbs aren't sticking. Thye're a bit tricky to get off as the screws are made of cheese so be careful, but I find one of them (the rear I think) has a tendancy to build up grot in the seat of the choke plunger.

Well it had a std can and DJd carbs and K&N and ran fine and I was getting 41-42mpg. Since I sold the K&N and stuck a std filter in its been pants. Hopefully the new carbs will work. Will give em a clean first.

Sent from my Galaxy S2 using Tapatalk

[johnnyrod]

Hopefully I'm not repeating stuff from the other thread(s) but if it's been on a track then i'm guessing it used to hav a noisy can (couldnt really see in your pic) hence the dynojetting but probably sold separately before you bought the bike. Pity they couldn't be bothered to undo the carb work as well and put it back to stock properly. Good luck with it! Provided the stock carbs are all they seem you should be fine, I used to get 55-60mpg out of mine when it was in stock form (I still get 50+ now). As a road bike, the extra power isn't really necessary.