'flat spot' in mid-rev range when accelerating?

Hi all,

I've got a 2010 SM with MRD/SSW, jetting and 3x3, which has developed a flat spot in the middle-rev range when accelerating. Seemed to just 'happen' mid ride a few weeks back. Until then the bike had been awesome.

The only thing that I can think of is that the cam chain has jumped a tooth and my timing is now out. The ACCT hasn't been doing it's job properly, and the chain's been making plenty of noise, perhaps it was very loose. I've got an MCCT going on this week, and will ask for the timing to be checked while in the shop.

Anyone got any ideas? :thumbsup:

I'm not familiar enough with the noise of pinging, and I can't hear much thanks to the pipe, but I could swear that there is a minor knocking audible from somewhere.

Still starts and stops as easy as ever.

I hope you haven't filled up with that 10% ethanol crap...

pinging is a tell tale sign of the octane rating in the fuel is not high enough..

try some high octane fuel and see how it runs then..

Also could have some water in your fuel..empty your carb fuel bowl...

If problem persists remove the carb and check for jet blockages

have you done the locktite fixes?


Thanks for the replies.

I have never fed the bike anything less than 98 rated fuel from Shell and BP, so unless I have been really unlucky, I should be ok there.

None of the loctite fixes have been done.

Have just take the bike to the mechanic today, who tells me that it will most likely be carb related, as the timing in his opinion is ok. He didn't want to touch the carb, as I couldn't tell him what jetting was installed by another mech. Fair enough, he said I would be paying hi to discover what has been done, when it would be cheaper to return to the original.

Time to contact the previous mech and see if I can get it looked at before Saturday!!!!

carb work is easy, and save yourself some money while learning your bike.plus you never know what some of these mechs do or miss in their rush, the hard stuff is understandable..everyone should be doing this, especially with this easy bike to work on.and all the help here.

Maybe when I have a garage, some tools and some time - that would be great! In the meantime I need to rely on others to make this stuff happen for me.

Unfortunately I live in an apartment block than bans any mechanical work on vehicles in the common areas including my own allocated car space.

If you choose to have a mechanic work on your bike ,always use the same one, as he will have a history of prior work done to your machine......

Though finding a good mech can be a challenge...

if you live on the ground floor you could roll it in your front door one night. you don't need many tools to remove and inspect your carb. make absolutely sure you put it back the way it was before. or just take it to a shop. if you find a good one always use the same mechanic, tip him too.

to bad you don't (i assume) have the tool kit that comes with the bikes as it has all you need to take the carb out. A phillips #2 screwdriver, a pair of pliers if the fuel line is hard to remove, and (darn memory) 8 or 10mm wrench for the throttle cables. I guess sockets to remove the seat and side panels could be handy too.

To open up the carb might need a screwdriver style impact driver (cheap)if the screws are hard to remove.

to remove the brass plug for the idle mixture a cordless drill would be handy.

Once you learn how it is done it is the kind of thing you can do in the parking lot at the motorcycle parts store, or the corner of a gas station.

Find a friend with a yard and give it a go.

MCCT installed yesterday, bike definitely a bit quieter now from that area.

Checked the oil yesterday, and was surprised at how low it was based on the small number of kilometres I have done since putting it in. Will have to keep an eye on that, as the bike isn't leaking/smoking at all.

Also managed to get a Friday booking at the original mechanic that installed the jetkit and modified the airbox. Hopefully all sorted for the weekend after some minor rework.

The oil will seem low if you are checking it cold, everybody has a different method but I believe that most let it warm up, take it around the block, then shut if off and check it. The oil will run down into the engine-thats why it seems low.

watch how tight you made the mcct, its not supposed to be super quiet, from what i've read that denotes overtightnes and premature chain life. Since there isn't constant pressure on the chain as before, it'll make a litlle noise with the mcct, mine actually makes a litlle noise at cold start up, and as the engine expands a little from heat it slowly disapates. Theres a point where the rattle barely goes away(thats where you stop), if you keep turning it in more, more rattle goes away and it gets really quiet, (that is too far )a few have made that mistake.

All fixed now:

"check bike bogging down under load and lacking power.

Remove carburettor, strip down, clean all parts and inspect. Reassemble and

refit to bike. Locate top diaphragm sticky, free up and test ride OK"

Also had the MCCT checked and OK'd for tension.

As always, thanks for the suggestions!

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