Sundial Moto Sports

Nasty Rattle at Idle . GT550
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Author:  Clarkie_10 [ Wed Sep 27, 2017 12:41 pm ]
Post subject:  Nasty Rattle at Idle . GT550

Hi Guys ,
my bike is a 1975 GT550 M .

Just had my engine refreshed , Crank balanced +newbearings , new big end and little end bearings , Barrels replated Nikasil all new gaskets etc so no expense spared as I wanted reliability .
Timing checked and carbs set all runs fine so far ( 50 miles ) max 50 mph !

However whilst running above 1000 RPM sounds great but when left to idle it has a nasty rattle noise ! almost clutch ? or starter dog maybe ?
almost as if centrifugal fault as disappears when revs rise !!!

Anybody experienced this or have any idea where I should look ??
would appreciate your help .
Also I've decided to run mine on Castrol Power 1 2t oil fully synthetic ! good or bad idea ?? :?

Author:  GTandcbr [ Wed Sep 27, 2017 1:07 pm ]
Post subject:  Re: Nasty Rattle at Idle . GT550

Couple of observations. The bike should be tickover at no less than 1100 rpm or it will start struggling to run which may cause your rattling. Some people adjust tickover to 1500 rpm. Make sure the carbs are balanced correctly as if one is pulling out of synchronization this may also cause your symptoms.
I use fully synthetic too but its a personal choice. There have been many debates whats best. I used mineral oil to bed in my rebored engine but it has iron liners. Then i went back to fully synthetic.

Author:  Alan H [ Wed Sep 27, 2017 11:03 pm ]
Post subject:  Re: Nasty Rattle at Idle . GT550

Personally I use semi synthetic 2t oil in all my triples. Putoline TT light, and run well. Full synth is a waste of money unless you have a track bike IMO, but the choice is yours.
Remember that they were designed to run on 70s tech mineral oils.

Re. the rattle, my 550s tick over at about 1100rpm and don't rattle.
I suggest you go for a run to get it properly warm, then with the bike ticking over on the centre stand, go round the engine with a long screwdriver - handle end touching your ear and t'other end touching the cases. Move the case end about and you'll pinpoint the noise. The driver puts the noise straight to your ear so you can get a better location of the rattle.
Try not to burn your ear, but if you do and tell us, don't expect sympathy!

After a rebuild, its easy for something to be 'just' not tight enough and need a tweak.

Author:  rngdng [ Thu Sep 28, 2017 4:23 am ]
Post subject:  Re: Nasty Rattle at Idle . GT550

Does it stop rattling when you pull in the clutch?

Author:  Clarkie_10 [ Fri Sep 29, 2017 12:51 pm ]
Post subject:  Re: Nasty Rattle at Idle . GT550

Hi Guys ,

Thanks for your replies , I did manage a quick spin around the block this evening then when I got back with her warmed up , I set the tick over upto about 1200 and left it idling for some reason it dropped below 1000 and started the RATTLE !!
I then pulled the clutch lever in and rattle gone after playing a little worked out that noise disappears when clutch lever pulled in half way !

So what do we think now ? clutch plates ? springs ? bearing ? anything else ?? :cry: :?:

Author:  Alan H [ Fri Sep 29, 2017 1:56 pm ]
Post subject:  Re: Nasty Rattle at Idle . GT550

That could be 'loose anything' really in the clutch department.
Take the clutch cover off and check nothing is loose.

Further thoughts on this one, my GT750 does similar - many do, and it tends to be the clutch bearing that's very slightly worn. Most owners set the tickover when warm so it doesn't rattle, and just hold the throttle slightly open when it's first fun, or at a stoplight until the engine warms up and the tickover is a tad higher.

Author:  GTandcbr [ Sat Sep 30, 2017 12:34 am ]
Post subject:  Re: Nasty Rattle at Idle . GT550

My 550 has always needed to be run until fully warmed up before it will tick over properly. I would be taking off the clutch cover as Alan says and just confirm all i's as it should be.

Author:  Clarkie_10 [ Sun Oct 08, 2017 1:44 pm ]
Post subject:  Re: Nasty Rattle at Idle . GT550

Just a quick update , 200 miles since rebuild and have found that as things are getting a bit of use and hopefully bedding in that just a little tweak of the tick over does appear to cure the rattle .
so thanks again for your help fellas .

Btw has anybody upgraded suspension front and back on a 550 ? I've not ridden a two stroke pogo stick before !! :D

Author:  sportston [ Mon Oct 09, 2017 8:17 am ]
Post subject:  Re: Nasty Rattle at Idle . GT550

Clarkie_10 wrote:
Btw has anybody upgraded suspension front and back on a 550 ? I've not ridden a two stroke pogo stick before !! :D

Excellent analogy! Made me laugh. There is another thread on here that details how you can modify the damping in the forks. Here is a link from it
and this is the thread
If you don't have progressive springs it may be a good idea to get some.
As for the rear set-up, there are many bolt on coilovers you can get on ebay. Hagon etc. I fancy getting a set of these
And I suppose you could always get a universal steering damper if that doesn't fix things well enough.
Before you shell out all that money though, make sure your headstock is not loose and that it moves smoothly and check that your swing-arm doesn't need new bushes. Make sure your spokes are not loose on your wheels and that you have no wheel bearing play. Make sure tyres are good and correctly inflated.
On my bike I have fitted a fork brace too.
And if none of that can ditch the suzuki frame and get a Rob North jobby for the price of a small house.

Author:  jabcb [ Mon Oct 09, 2017 6:34 pm ]
Post subject:  Re: Nasty Rattle at Idle . GT550

Check to see that the tires are seated correctly.
There should be a circumferential line or series of lines molded into the tire sidewall near the rim. The line should be the same distance from the rim all the way around the tire & on both sides.

Is it pogoing at around just one speed?
My 72 GT380 cafe project pogos a bit around ~40 mph presumably because its not quite balanced perfectly. (A job for next year.)

My 75 GT550 forks are too stiff but don’t really pogo. The shock are from Progressive Suspension.

For best upgrade results on your GT550 for reasonably money, its worth considering Hagon shocks set up for your weight.
The stock fork springs are too stiff — see the ozebook link for good info.

Author:  Clarkie_10 [ Sat Oct 14, 2017 11:38 am ]
Post subject:  Re: Nasty Rattle at Idle . GT550

Once again thanks chaps for your recommendations ,
I've just had new wheels , forks re-chromed / rebuilt and fitted new swing arm bushes .

So think I will save up some penny's and buy some goodies ! or put it on my xmas list for old mother christmas !! :lol: :lol:

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