Triumphrat

andre12a · 11-05-2012, 04:48 PM

Hi

I have some unusual valve clearance readings I thought I might get some opinions on from you learned fellow Triumph riders.

My bike is a Thunderbird 900 2001 model with 80000 kilometres (50000 miles) on the clock.

I'm getting .10 mm (.004 ins) on the inlet No 1, 0.0mm on No 2, and .05 mm (.002 ins) on No 3. I intend to bring these all back to .15mm (.006 ins).

The exhaust side is where I have some concern.

No 1 and No 2 are reading .10mm (.004 ins) , but No 3 has two quite different readings. The outside valve is .08 mm (.003 ins) , but the inside is .21 mm (.008 ins).

Any ideas about why I would have one that is showing such a large gap. I suspect a stuck valve but I am up for suggestions.

thanks.

Peter

IrlMike · 11-05-2012, 05:09 PM

The 12 valves & valve seats will all settle or wear individually, so nothing odd with your readings.

IMO the valves are better off set at the lower spec of the service data range. ie inlets nearer 4 thou, exhausts 6 thou. There is less impact loading then thru' the whole valve train. It is explicit that Triumph expect such settings to not fall too tight for proper operation for the following 12k miles even when set at the lower point.

lovecuba · 11-05-2012, 05:49 PM

The inlet valve settings can have more leeway in respect to tighter than recommended settings due to them not being at risk of burning out. But the exhaust settings need to be within manufacturers minimum settings i.e. the gap must not be less than 0.15mm.
I would tend to remove the cams and get your clearances back closer to stock and remove that large disparity in the various gaps.

andre12a · 11-06-2012, 02:20 AM

Thanks. I will reset at the lower end and remove the disparity as per your suggestions.

tommyturbo2 · 11-06-2012, 10:24 PM

Andrea12a: Not to say that Mike and Cuba are wrong, but I have a little different take on valve settings. My experience based on about 22K miles of ownership of my 98 TBS strongly indicates a tendency for the clearances to tighten up over the 12K mileage service interval. This may be due to the degree of strain placed on the valve train based on more aggressive riding. Mike and Cuba both prefer the tight end of the clearance to decrease impact loading on the cam follower. I set mine at the wide end of the spec (which should allow for a thicker oil film between the cam and its follower). This setting tends to minimize the chance of the clearance getting too tight potentially causing a burned or warped valve. My first valve adjustment at 8K miles had the valves all at the tight end of the specs except for #3 exhaust and #2 intake. They were under spec by .002", and contributing to unstable idle. I reset all the valves at mid spec, got a nice stable idle, and no significant unusual valve train noise. At 20K miles the unstable idle had returned, and upon checking, #3 exhaust had barely enough clearance to allow rotation of the cam follower. I reset all the valves at the wide end of the specs, and now the engine has an excellent smoother idle than ever before. A thousand miles later I rechecked the specs and they were the same. I then installed green cams and reset all the clearances to max specs, and the idle is excellent again. So, that's my two pence, and I'll probably check the new cams clearances at about 26K miles. Cheers, tommyturbo2

andre12a · 11-07-2012, 02:32 PM

Thanks tommy for your input. At the moment I am struggling with how to get a seized torz bolt off the alternator so I haven't put any more thought into the valve settings. I think I am going to have to make up special tool for the bolt so I can get the impact driver onto it. As for the valves, I will take all advice into consideration when i get back to them. I am still unclear about how I have such a big gap on one exhaust valve. I'm thinking I should do a compression test on all cylinders to see if there might be some reason for this.

lovecuba · 11-07-2012, 03:52 PM

I agree with TT in respect to the wider clearence due to the propensity of exhaust valves in particular to recess. As mentioned in a previous post have just checked clearances on the TBS with all the exhaust gaps @ 0.178 except one @ 0.152.
The inlets were @ 4 x 0.127 1 @ 0.10 and another @ 0.760
So, as can be seen one gap needed attention. Rather than pull the cams to sort this one (inlet) gap out I have decided to run another 5-8000 miles and will check again then bring all the clearences up to widest spec.

WSC · 11-07-2012, 04:14 PM

+2 on the wide side of the tolerance. All normal wear parameters tend to reduce clearances and the cam profile is designed so that there is no real impact loading; when the cam contacts the tappet (actually the shim) it is on a mild part of the ramp and there's really no shock to any of the parts. The heavy lifting comes later.

moonshinerunner · 11-11-2012, 12:11 AM

G'day
Don't worry about the difference between two valve clearances on one cylinder. I done my 100,000km's (60,000miles) service and had similar measurements on my exhaust valves and intakes. Example is one side I fitted 2.64 and the other valve 2.70, I was worried also and did a compression check after just to be safe , you know stuck valve but all OK. While I had the cams out I replaced the cam chain and removed all shims and wrote down the measurements for next time and where they fit eg No1 cylinder left 2.70 right 2.64 etc . I drew a picture and put the shim sizes in the little circles. two circles for intake two for exhaust and one bigger circle for the piston. Now put that away in my A4 folder for the bike. ready for next time.