Valves or maybe carb

Hi folks,

I've got a 2008 FE550 that is running well but could be better. I had quite a loud top end rattle so I checked cam chain tensioner, it has about half way left to go. I checked and adjusted valve clearances to 1/6th turn. The intakes were perfect but the exhausts were way loose, I didn't count but they were probably close to 1 full turn out. After this adjustment, the rattle was totally cured. But it introduced a popping/backfiring on deceleration that I never had before.

I hadn't ridden the bike in a couple of months before this so I'm wondering if the popping is the bike running lean because of colder winter air? I played with the fuel screw but didn't make any difference.

Other things that may be related - I have a bog when I stab the throttle at idle or at low RPM (I found a tutorial about checking/adjusting the accelerator pump that I am going to follow), and this is kinda hard to describe... but first and second gear feel like they don't have much go in them before they top out and they are kind of tinny and rattly. Then third and fourth gear pull my arms out of their sockets and feel full and healthy.

Any ideas or suggestions about any of this much appreciated I was looking at the Taffy carb kit, might give me a better running bike and fix some of these issues at the same time??

Cheers

WArdogG said:

Check the can follower bearings, they tend to destroy the cam and sometimes you get a broken rocker arm just for good measure. Valve clearance becomes tighter over time, not loose, unless the lock nut on the tappets come loose. A worn follower bearing could be the reason the clearance was larger, unless of course it was set like that before...

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Cheers WArdogG, looks like there is space to get the rocker cover off with the engine in the frame?

ned37 said:

never removed the radiator on any of them.
while you're in there, visually check bearings on the cam

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Thanks folks. The only bearings I see in the schematic is #15 here, are those the ones you mean?

Taffy said:

you need to start with an extended pilot screw (EPS) and fit it under the carb. adjustment of this will probably cure the popping

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Thanks Taffy and Ned.

I've played with the fuel screw in the carb a bit, using these notes I made for myself:


The approximate range of the fuel screw or fms (fuel metering screw) is 1 & 3/8 turns open to 2 & 1/8 turns open. If you are less than 1 & 3/8 turns open you need a smaller pilot, and if you are more than 2 & 1/8 turns out you need a bigger pilot.


1. Check current position of fuel screw (I was 1.5 turns out)
- Opening the fuel screw adds more fuel
- Closing the fuel screw adds more air
2. Screw should be between 1.4 and 2.25 turns out
3. If the screw needs less than 1.4 turns out, mixture is rich
- Need smaller pilot jet (and maybe other jets)
4. If the screw needs more than 2.25 turns out, mixture is lean
- Need larger pilot jet (and maybe other jets)

But basically all I did was open it up to 2.25 turns out to try and combat the lean mixture and hopefully stop the popping on decel, but it still pops. Am I on the right track?

Cheers

WArdogG said:

No, check the scematic for the valves
On each of the rocker shafts is a cam follower bearing.

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Hey, I've looked at the parts fiche but there's no mention of a bearing anywhere, is it part #55? That is listed as 'end cap' for the rocker shafts. Cheers

bergbro said:

If you look at the rocker arm (box with 62 63 in it) one end has 2 tappets adjustment screws. The other end has a shaft with a bearing that runs on the cam. The bearing that runs on the cam is what people are suggesting you look closely at as they are prone to fail.

Books can be handy but sometimes you need to get your hands dirty to understand what is going on. Best to pop the top and have a look at those roller rockers (another name for that type of acctuation system).

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Thanks bergbro, yep that's for sure! Adjusting tappets is as far as I've gone before, taking off the rocker cover will be a first for me. Am I right in thinking I can check these cam follower bearings, as well as the cam bearings themselves, without breaking the cam chain and lifting the cam shaft out?

Thanks lads that's great. Are either of these sets of bearings a wear part that I should replace even if they look OK? Bike has 120 hours. I'm aware that if they roll OK and aren't visibly cracked or deformed, I might not see a problem that somebody more experienced would see and maybe best just to replace them.

Ahhhh the joys of knowing just enough to be dangerous, but not enough to be effective

Taffy I found item 100106 on your site, is that not the right bearing?

Cheers