cams facing where ?

[ffjoe]

I'm doing my 52,000 mile valve adjustment. My dilema is this. The manual states that when #1 cylinder is at top dead center you will see the timing mark through the viewing hole and the cam lobes will be facing away from each other. Mine lean in towards each other. When turning the engine 180 degrees and so forth it all works out that when you hit #3 cylinder you see the other single timing mark so I guess I'm doing it right. I noticed this last time nd chalked it up to a mispraint in the manual. Anyone else experienced this?

[dingy]

This is my humble opinion on measuring the valve clearance, may not be the majorities opinion.

 

I don't believe that you have to be at TDC to get an accurate measurement of clearances. As long as the cam lobe is pointed away from the valve shim, the measurement should be very close.

 

The cams are a very high precision machined part. Once you roll the motor through the point of the lobe contacting the installed shim, lets say 15 degrees past, the clearance should remain constant until the cam is rotated enough for the lobe to again be close to re-engaging the installed shim on the opposite face, again 15 degrees prior to contact.

 

Another engineering term for this is concentricity of the cam lobes radii to the cam bearing surface. This dimension will be a very close tolerance number.

 

The cam lobe radii at the center, not at the lobe tip, are ground using center points that are on both ends of the cam. Also ground using the same points are the bearing surfaces. This should, in 'theory' maintain a close concentricity of these surfaces.

 

What that means is, as the cam is rotated with the lobe not in contact with the shim, the distance should not vary significantly.

 

I will put my flame suit on now.

 

Gary

[BuddyRich]

I basically do mine when the lobe is pointing up. Seems to work out the same as in the book.

[djh3]

I somewhat agree with the "pointy part away" theroy. ME thinks the biggest reason for the "TDC" rule of thumb is a consistant measring point. Match the "TDC" up rotate one time match mark again etc, you "should" be measuring cams in identical locations of travel. I belive the theroy is correct if you have been around engines and understand them that if the lobe of the cam is away from the contact surface it is disengaged. With that said I use the ole tried and true TDC methiod too. As for actual experence on these things. I aint been there yet, my FJ 1200 wasnt to bad.

[spike13]

think the answer to your question can be found here http://www.venturerider.org/forum/showthread.php?t=38545

[etcswjoe]

think the answer to your question can be found here http://www.venturerider.org/forum/showthread.php?t=38545

 

 

 

I followed this on my first one and it worked well.

[ffjoe]

think the answer to your question can be found here http://www.venturerider.org/forum/showthread.php?t=38545

I see he made the same observation as me, the cam lobes won't face away from each other at TDC. I just found that curious and wanted to make sure I didn't have an issue. Thanks.

[kyle]

at 52,000 miles let us know which valves needed new shims and how much they were outta spec. I did my first at 46,000 and had only one "#2 inside exh." was outta spec. by only .02. amazing how tough these engines are.

[MikeWa]

This is a 4 stroke engine which means #1 cylinder will be at TDC twice. Turn the engine 360 degrees and see if things line up.

Mike

[ffjoe]

at 52,000 miles let us know which valves needed new shims and how much they were outta spec. I did my first at 46,000 and had only one "#2 inside exh." was outta spec. by only .02. amazing how tough these engines are.

Cylinders 1 & 3 intakes and 2 exhaust shims were at thier limit so I replaced them. I also did it at 26,000 miles and replaced some. You can only purchase shims in .005 increments unlike what you find in the bike from the factory. Better loose than tight. At least with valve clearances.

[Mel]

This is a 4 stroke engine which means #1 cylinder will be at TDC twice. Turn the engine 360 degrees and see if things line up.

Mike

 

TDC usually means top dead center on the COMPRESSION stroke, thereby having both valves fully closed. If you turn the engine 360 degrees, you can bring the piston to the top on the exhaust stroke, but depending on the cam timing, dwell, lift, etc. you will not have both valves closed. My experience in the past tells me it's difficult to keep the piston at the top on the exhaust stroke because the pressure from the valve springs wants to keep the camshaft/crankshaft turning.The timing mark should be obvious when on the compression stroke. Whenever possible I used a dial indicator through the spark plug hole to the piston to assure TDC.

[MikeWa]

TDC usually means top dead center on the COMPRESSION stroke, thereby having both valves fully closed. If you turn the engine 360 degrees, you can bring the piston to the top on the exhaust stroke, but depending on the cam timing, dwell, lift, etc. you will not have both valves closed. My experience in the past tells me it's difficult to keep the piston at the top on the exhaust stroke because the pressure from the valve springs wants to keep the camshaft/crankshaft turning.The timing mark should be obvious when on the compression stroke. Whenever possible I used a dial indicator through the spark plug hole to the piston to assure TDC.

 

Agreed TDC generally refers to the compression stroke. Not always but usually. Problem is all of the marks on the crank will line up at both positions, compression and exhaust. The piston will also be at top at both positions. So it is not always easy to tell if you are on compression or exhaust. The only visible difference will be the cam positions. So if you are doing a service which exposes the cams and they are not where you expected at TDC try turning the crank 360 degrees. The cams may come into alignment. This is just a suggestion and certainly will not solve all problems but it may help sometimes. Also you can sometimes find TDC by lining up the cam timing marks.

 

Mike

[MasterBruce]

Notwithstanding the comments, but turning engine to 30 degrees will not work at all. Cylinders need to be rearranged in order to match with TDC.

[RandyR]

Cylinders 1 & 3 intakes and 2 exhaust shims were at thier limit so I replaced them. I also did it at 26,000 miles and replaced some. You can only purchase shims in .005 increments unlike what you find in the bike from the factory. Better loose than tight. At least with valve clearances.

 

You can buy 25mm shims for the Triumphs in .025mm increments. The current air cooled Triumph Bonneville variants and the Thunderbird as well as the older 900/1200 Hinckley engines all use 25mm shims the same as our V4 Yamaha bikes. Used shims from the factory can be in any .01mm increments.

Edited January 3, 2013 by RandyR
Dingy made me do it.

[dingy]

Used shims from the factory can be in any .001mm increments.

 

Maybe .01mm increments ????

 

.001mm is .000394" which is well below the ability to check with standard feeler gauges.

 

 

Gary

[djh3]

When I was doing FJ 1200 Legend car motors I would pull out some odd numbered shims. Why the factory would have say a .027 and aftermarket all you could find would be say a .025 or .030. (decimal place not withstanding) Its a good thing I had the chart to be able to say "OK there is a 27 in now and I need to be @ XX so I need a XYZ size" I have a plastic bag with quite a few shims. I kow I have a few over the 300 range. I allways figured if you neede them the valve was a bout to be pulled thru the head.