Good vibrations

Message

szrdave · #1 Post by **szrdave** » Fri Mar 04, 2011 12:38 pm

Or not!

I've got a vibration that runs from 4-6krpm, not heavy but just about noticeable on a light throttle.

The bike also tries to shake itself to bits when pulling low revs at low speed, even on a neutral throttle, and is quite weak at idle and will stutter and cough back through the airbox occasionally when opening the throttle from idle/at low rpm and occasionally stall.

I just changed the manky air filter, which has perked the midrange up a bit but not affected the low rpm running.

The bike pulls cleanly and strongly once into the revs and is plenty quick enough.

Could these issues be related, or are any a characteristic of the bike?

The throttle bodies were balanced in 2008 according to the service history, and only 5k miles have been put on the clock since then, there was also a note that the ex. valve clearances on the rear cylinder were on the spec. limit at the time.

My commute is only 3 miles long, and it's better when warm. Turning the idle up to just over 1500 rpm has cured the stalling but is only masking the problem. When out of town everything is fine and the bike runs beautifully

Aladinsaneuk · #2 Post by **Aladinsaneuk** » Fri Mar 04, 2011 1:05 pm

What Tyres and pressures?

Are the bar ends tight?

szrdave · #3 Post by **szrdave** » Fri Mar 04, 2011 2:10 pm

Tyres - Diablo front, 021 rear. Both pretty worn.
Pressures - A couple of PSI below book (by choice)
Bar ends - Present and tight

Tbh I'm fairly sure it's an engine rather than chassis issue, the 4-6krpm vibes occur in every gear and the low rpm/high gear vibes are a symptom of the engine struggling.

One thing I forgot to mention is there are aftermarket cans fitted but I presume the chip hasn't been changed.

anzacinexile · #4 Post by **anzacinexile** » Fri Mar 04, 2011 9:07 pm

Rough at the bottom end is usually cured with a good TB balance. I find she runs a lot smoother if the front cylinder is pulling slightly harder than the rear when setting up the balance. Also, make sure your TBS is set right ACCORDING to the book (not as simple as simply setting 0 on the dash)

Given all that though, the big twins dont like pulling hard at low revs. Keep her above 3K minimum before giving her any berries

D-Rider · #5 Post by **D-Rider** » Fri Mar 04, 2011 9:50 pm

Yep - check your plugs are clean, gapped properly and none of them have worked loose (yep I've had that happen) and balance your TBs.

Bet it will all be lovely after that.

szrdave · #6 Post by **szrdave** » Sat Mar 05, 2011 11:44 am

The plugs on the rear cylinder are good, I'll check the fronts too to make sure.

TB balance sounds like the next step, although there is no point in doing it before the valve clearances are adjusted.

Which brings me on to another point, how much will a dealer normally charge to do clearances on the rear cylinder?

I have always done them myself on other bikes (and still do on the SZR, aren't screw and locknut valves easy to do by comparison!) but don't have a garage to work in now

I will check the clearances first though, in case the front cyl. needs doing too.

Samray · #7 Post by **Samray** » Sat Mar 05, 2011 11:57 am

Which cans are they?

szrdave · #8 Post by **szrdave** » Sat Mar 05, 2011 12:47 pm

Stock headers, 'Redline Performance' cans which are straight through and bloody loud

They also 'tastefully' fade from black to red!

Samray · #9 Post by **Samray** » Sat Mar 05, 2011 1:07 pm

I know fa bout falco's but on my bikes I'd expect them to leave it running rich and expect those symptoms.

along with sooty pipes

D-Rider · #10 Post by **D-Rider** » Sat Mar 05, 2011 1:40 pm

You'll be hard pressed to find people that have needed their Falcos valve clearances adjusted - ever.

Yes one or two will pipe up and it is wise to get them checked at the appropriate services but it's not that likely you'll need to have them re-shimmed

szrdave · #11 Post by **szrdave** » Sat Mar 05, 2011 1:55 pm

That's interesting D-Rider, the last service includes a note saying they're at the limit. Time to break out the feeler gauge and check them myself!

On a brighter note I should be having a new set of tyres and an Ohlins shock fitted next Saturday

anzacinexile · #12 Post by **anzacinexile** » Sat Mar 05, 2011 8:27 pm

szrdave wrote:That's interesting D-Rider, the last service includes a note saying they're at the limit. Time to break out the feeler gauge and check them myself!

On a brighter note I should be having a new set of tyres and an Ohlins shock fitted next Saturday

One of mine was on the limit at 9K. Now at 50K and guess what, still on the limit

szrdave · #13 Post by **szrdave** » Sat Mar 05, 2011 9:03 pm

That's good, saves me an afternoon of messing about.

Can you pm me your address so I know where to send the bill if it all goes pear shaped?

D-Rider · #14 Post by **D-Rider** » Sat Mar 05, 2011 9:07 pm

szrdave wrote:That's good, saves me an afternoon of messing about.

Can you pm me your address so I know where to send the bill if it all goes pear shaped?

As I said before .....

D-Rider wrote:....... it is wise to get them checked at the appropriate services but it's not that likely you'll need to have them re-shimmed

szrdave · #15 Post by **szrdave** » Sat Mar 05, 2011 9:15 pm

Lol, I was only joking.

It's good information though, as it's put my mind at rest to leave the job until the weather warms up.

Nothing better than being outside working on the bike on a nice warm sunny day! Less chance of making a silly mistake due to impatience/cold fingers too.