7000 RPM Stutter

[Timbollew]

Hi guys, Haven't been on for a while hope everyone is well. Finally got the bike MOT'd after my issues with the ignition electrics (sidelights not working) and it's developed a stutter.


It's strange because if I ease the revs up it'll go past the 7000 mark with no issues (most of the time) if I open it up quickly it's guaranteed to stutter. On the flat it'll work it's way up slowly through the revs but it's like a bad misfire.


I've had the plugs out and give them a clean and they seem to be sparking OK, I changed the air filter as it hadn't been done in yonks but still the same. The rubbers on the carb seem pretty badly cracked so I'm thinking it's sucking in air through here when the revs are peaking but low revs not enough pressure to take in the air like I say normally problematic around 7000 and sometimes around 4000. My theory is just that a theory can anybody give some suggestions on how I could check this? Also I imagine the inlet rubbers will be pricey anyone know of deals/cheap fixes?


Thanks guys.

[anutz]

have you checked the carbs balance???


you can check the pressures with a range of gauges, that may show if you are lacking pressure at intake???


Anutz

[darrsi]

I've had the equivalent of an air leak from the carb rubbers before (one folded in on itself when refitted), and it made the bike bog down on hard acceleration, rather than stutter.

[anutz]

Carb Sync tool i used but there is a good guide posted some where i followed, they used different type of gauge...still worth a check to see if the pressures are off/out of sync..


http://foc-u.co.uk/index.php/topic,15985.msg184147.html#msg184147


Have you looked at the fuel filter?


What about the TPS?

[Timbollew]

I guess it could be classed as bogged down. Basically when it happens the engine starts making a strange noise like its misfiring or something and the power I'll climb very slowly until it gets to a point the revs won't go any higher. I can ride ok but as soon as I get to an overtake situation I've got no confidence because the issue might just kick in and leave me stranded without power.

I don't have a carb tune unfortunately so can't check the balances might need to have a look into getting hold of one. The checks you're referring to are these based on using a carb tune or compression test as I do have access to a compression test.

[Timbollew]

Sorry Anutz you replied while I was typing. I'll try and get my hands on a carb tune as I'm fairly sure they need balancing anyway. I'm just looking at some secondhand ones on eBay but can only find 2 cylinder ones. Can I use a 2 cylinder and just switch the pipes around?

[darrsi]

You need to check the TPS before doing a carb balance anyway, only takes a minute to see if it's in the right position or possibly faulty.
I've had 2 of those break down on me before, and the bike tends to feel as if it's just not happy with itself, especially at lower revs where it can feel a bit jerky.
Difficult to explain really, but i can sense now even when it's not positioned correctly, although the readings can also be false as well just to make things even more tricky, as both of mine started to break down rather than simply stop working, which would've given me a blatant reading of 3000rpm. 

[Timbollew]

My TPS was out so I've adjusted now. Just waiting to get out on it to see if any improvement. Buggers not starting now which is weird as I only took the plugs out and give em a clean. Just put new plugs in and drained the float bowls to rule out water in there but not starting. Just put battery on charge as it took a beating me trying to start it so hoping fresh charge will wake it up.

[Timbollew]

Let's safe to say I have the confidence to overtake again I think it was the TPS but the new plugs and air filter have helped.