xs cam timing

[clarknobb]

I need the stock camshaft timing figure for my xs. they will be written as valve open / close BTDC / ATDC. I want to dial in my cams for increased horse power. I know how to do this but need the figures to give me a start point. Anybody help? Cheers Nobby.

[skids]

Re: xs cam timing

The arrows on the cam bosses (just to the left of center) should line up with the dot (actually holes I think) on the cams at TDC. Does that help?

Originally posted by clarknobb
I need the stock camshaft timing figure for my xs. they will be written as valve open / close BTDC / ATDC. I want to dial in my cams for increased horse power. I know how to do this but need the figures to give me a start point. Anybody help? Cheers Nobby.

[strom]

...when the crank is on T. Take out the plug off 1. or 4. cyl, should be on top.

LP

[Ken Talbot]

Nobby - are you talking about changing the actual profile of the lobes i.e. building them up, grinding back down to a different shape?

[clarknobb]

I should have been clearer in my request. Stock cams as they come from the factory are usualy a couple of degrees either side of the specified cam timing figures. So by rephaseing them to the exact specified point at which they begin to lift the valves, you get spot on cam timing. this is known as "degreeing in " or "Dialing in cams " it involves a simple math formula. a degree disc and pointer on the crank, a positive stop in the plug hole and a dial guage to measure the precise valve lift.
What I need are the factory specifications for cam timing. that is to say when the designer of the engine intended the cams to start lifting. once armed with this info I can then calculate how far adrift the manafacturing tolerance is and reset the cams by sloting the sprockets. its usualy worth a couple of horse power, and is part of so called "engine blue printing". Once done I will write a step by step guide a publish it here. Thanks for the input so far. Unfortunatly you cannot measure the timing as it is and use that as your start point, as it is NOT what the designer intended. Youll just end up chasing an error around your cylinder head for ever, oh and youll bend most of the valves in the proccess. sounds horifficly complex but is childs play once you have the stock settings. Not in the Clymer manual. a pal of mine is looking up Yamaha Specs at the factory, maybe sombody has the info in another manual? Nobby.

[uk1.1s]

Valve timing

Nobby,

Have a European XS1.1 sport Yamaha factory manual suppliment with me here at the moment and there are extensive data tables which include some on ignition timing, in the form of retarded data and an advance timing graph (bike has the vacuum advance module it that helps and is a UK 81/82 model).

I have - ignition timing retarded 5 deg at 1100 r/min (no tolerance range quoted).

Ignition timing advanced - 1 deg at 1800 +/- 100 r/min and 30 deg at 3900 +/- 300 r/min. Curve is flat after this - therefore fully advanced after 30 deg. Advance graph is a straight line between 1800 to 3900 r/min, so a linear rate of increase.

As I understand it the 'XS11 Sport' had slightly lumpier cams, so this may be a little different if Yamaha were bothered to change other things to suit. I have a standard XS 1100 factory manual at home - will try to remember to look up the data there to check it's the same or let you know differences.

Give me a prod with a Private Message or email if you're still interested and I've not come back to this thread - as it's a damn busy week this week!

[chopper]

there is no information on cam profiles,valve phasing/overlap etc that i can find in the factory manuals...only thing i can suggest is degreeing your cams by slotting the sprockets..very slowly in small amounts...or check for aftermarket cams,these were available back in the day.as graham said the xs1.1s has a different profile,same valves etc,carbs are different internal spec,peak torque is moved down to 4000rpm,merriam cycles may be able to help you with the valve phasing/overlap degree figures? they seem very knowledgable

[clarknobb]

I am now determined to find this info. GSXR suzukis and the like have this info available so why not the XS? As I mentioned earlier, though in theory its possible to improve things by guesswork the actual figures I am after enable me to determine LOBE Centre. as intended by the factory.
Anyway, Input thus far is much appreciated, we will get there!
Cheers Nobby.

[chopper]

"Adjustable cam sprockets
Most riders know that performance camshafts require the correct cam timing to obtain reliability and maximum gain in power, but even stock engines will benefit from precise cam timing, we have found substainal gains in power by degreeing the cams in, many bikes roll off the production line with a stack up of tolerances that lead to the camshafts being several degrees out of the desired position, add camchain stretch, wear on the guides and even more power is lost." this is from a leading tuners website,may help explain this thread

[chopper]

[i]Originally posted by chopper this is from a leading tuners website,may help explain this thread [/B]

How to degree in camshafts
Why Degree in Camshafts
In a stock engine, even the latest new sports bike, each part has been manufactured and assembled within a fine tolerance, but each component put together will lead to a stack up of tolerances. Where the piston is in the bore and when the camshaft lobe is opening the valve will depend on many parts such as crankshaft journals, camchain, sprockets, the camchain guides, camshaft journals, camshafts, cylinder head, gaskets, valve clearances etc. As the engine is run, even the slightest wear will increase this stack up of tolences. Camshaft degreeing or blueprinting as it is sometimes called, will counter this stack of tollerences and uncover some hidden horsepower thats locked up in almost every stock engine. If you have bought performance camshafts you should degree them to the manufacturers specification or you will not be getting the full performance gain for the money you have just spent, you will also comprimise the reliability of the engine. With a few basic tools, the knowledge and a pair of adjustable camshaft sprockets, you can degree in your camshafts to gain extra power that costs you nothing.

Finding Top Dead Centre

The first thing you will need to fit is a degree disc to the crankshaft, Debben Performance can supply this, part number W1012, this disc has a large diameter for easy reading and is made from alloy to last. A degree disc can also be used for precise ignition timing.Bolt the degree disc to the generator side of the crankshaft so that you are free to rotate the engine from the ignition side. Never rotate the engine by the bolt holding the degree disc incase you disturb the position of the disc. Now you will need to make a pointer to line up with one of the increments on the disc, you could make a pointer from a peice of welding wire or a coat hanger with one end ground or filed to a point. Attach your pointer to the engine with an engine case screw, the pointer should not move easily or rub on the degree disc but should be pointed towards the increments as close as possible. Finding Top Dead Centre or T.D.C. is the next job, the T.D.C. marks on your ignition side of the engine will not be accurate enough. T.D.C, or more precisely 0 degrees, is not only where the piston is at the top of the bore but where the con rod is also perfectly central in the bore, while the piston is parked at the top of the bore the crankshaft will rotate a couple of degrees with only the lower end of the con rod moving. To precisely find where T.D.C. is you will need a Positive Stop Tool, also available from Debben Performance, part number 99288 for 10mm spark plug holes as on most GSXR750s, 99286 for 12mm holes as on most 16 valve Suzukis, Kawasakis and Hondas and 99287 for 14mm holes as in the early aircooled Suzukis and Kawasakis. This is a tool that screws into the spark plug hole and stops the piston from reaching the top of its travel. Rotate the engine clockwise slowly until the piston gently lands against the Positive Stop, look at your degree disc and jot down the figure the pointer is pointing at, this is your before T.D.C. figure. If the engine is now rotated in the opposite direction the piston will again be stopped in exactly the same part of the bore, jot this figure down and now you have your after T.D.C. figure. As the degree disc has yet to be positioned in exactly the right place, you may find that you have for example 32 degrees before T.D.C and 48 degrees after T.D.C., whatever 2 figures you have should be added together, this total is then halved to give the correct before and after figures. In this case 32* before + 48*after = 80, half of 80 = 40*, so we would need to reposition the degree disc without moving the crankshaft so that the pointer pointed to 40*. We would then repeat this proceedure to make sure that the piston stops at 40* before T.D.C and in the opposite direction at 40* after T.D.C.

Now you have accuratly established T.D.C. or 0 degrees. You must take care while rotating the engine forwards and backwards, always remove all of the spark plugs and make sure the inlet valve is not forced into the Positive Stop Tool. If you have disturbed your pointer or the position of the degree disc on the crankshaft you must repeat this proceedure.

Degreeing Camshafts

You will need the cam timing specifications, these are printed in workshop manuals for stock bikes or are included with performance camshafts, take care not to loose the spec sheet if you buy a performance camshaft, with out these specifications nobody will be able to time the camshafts accurately or reliably. The 'ramp' of a camshaft lobe is designed to gradually open and close the valves, if the ramp was not gradual, the valves would be banged open and slammed shut, this would result in valve bounce, high wear and be mechanically noisy. The problem is that this ramp makes measuring the exact point at when a valve is opened almost impossible to establish. This is why valve opening and closing times will be stated at a certain amount of valve lift in performance camshaft spec sheets, the amount of valve lift (movement of the valve from its seat) is easily measured with a dial guage placed to read from the top of the valve follower, bucket or spring retainer (but not rocker arm). Debben Performance can supply a dial guage for £56.95 + vat, Valve lift should also be measured with no valve clearance.

The exhaust camshaft should be degreed in first, as the exhaust cam will change the timing of the inlet cam, the inlet cam should be degreed last. Mount the dial gauge so that the plunger is in line with the valve and reading zero lift when the camshaft lobe is pointing away from the valve, as you rotate the engine the camshaft lobe will start to move towards the valve and then start lifting the valve from its seat, the dial guage will also start to measure the lift, when the dial guage has measured the amount of lift specified in the cam spec sheet, stop, you now need to jot down the figure that the pointer is pointing to on your degree disc, this is your Exhaust cam lobe opening figure and is usually X of degrees Before Bottom Dead Centre. Continue to rotate the engine until the valve has fully opened and is on its way back to the valve seat, the guage needle will have reached a certain point and be returning towards the amount of lift you took your opening figure at, if for example this was 0.30", stop and jot down this figure, this figure is your Exhaust cam closing figure and is usually X degrees After Top Dead Centre. Continue rotating the engine and make sure the dial guage reads zero again when the valve has finished moving.

Now you have 2 cam timing figures, you can work out the Lobe Centres

Lobe centre = the larger figure + 180, then subtract the smaller figure and divide this total by 2

For example

if your Exhaust cam lobe opening figure was 60* Before B.D.C and your Exhaust cam lobe closing figure was 21* After T.D.C then 60* (the larger number) + 180 = 240, take away 21* (the smaller number) 240-21=219, half of 219 = 109.5, so now we know 109.5 as our current lobe centre figure

If you are dialing in stock camshafts, the workshop manual may not state at what amount of valve lift the cam degreeing figures are taken, in this situation you could use this equation to work out the lobe centre figures using the manuals opening and closing figures

For example a Honda Fireblade manual says

Exhaust opens @ 40* Before B.D.C.

Exhaust closes @ 10* After T.D.C.

40* (larger number) + 180 = 220, take away 10*(smaller number)=210, 210 divided by 2 = 105 so 105* would be the lobe centre figure to aim for

Take your degreeing figures at 040" of valve lift and when you have the opening and closing figures, run them through the above equation, if you end up with for example 109.5* lobe centres, 109.5* would be 4.5 degrees from the 105* you are aiming for.

To adjust the cam timing, slacken of the exhaust cam sprocket bolts and rotate the crankshaft (without moving the camshaft) in this example 4.5 degrees, then tighten the cam sprocket bolts with the sprocket in its new position ( the cam sprocket would have rotated but the camshaft should have stayed still). Repeat the measuring of opening and closing to make sure that your figures end up equalling 105. Once you have the exhaust cam giving the right lobe centre figure, torque up the cam sprocket bolts and use loctite, then you move on and duplicate the process on the inlet cam, the inlet cam may have a different lobe centre figure to the exhaust camshaft.

For example the Honda Fireblade manual says

Inlet opens @ 15* Before T.D.C

Inlet closes @ 35* After B.D.C

35 + 180 = 215, 215 - 15 = 200, half of 200 = 100, so the inlet cam lobe centre is 100 degrees.

If at any time during the proceedure, the engine does not rotate easily, do not force it, you could damage a valve or piston if you do.

[clarknobb]

Exactly, now all I need are the stock figures........Nobby.

[uk1.1s]

Dialing in the XS11

Nobby,

The XS11 Sport suppliment does seem to have some cam cross section information - but not sure if that's any good to you. Let me know, I'll look it up.

As prediced - I forgot to pull out the stock manual to check for differences - 0/10 - will try harder .

Great information from Chopper (for me) as I'd always vaguely known why slotted performance cams work and why they do... but the details above give a much better understanding - thanks Mick

Don't know if you're in the UK - but if so, try calling Steve at Colourcoat up Lincolnshire way (Market Rasen I think). He drag races (or raced) an XS11 and has spoken to me a few times. Seems to be a wealth of information on the performance side of things.

His other interesting mods are FZR750 carbs (with altered inlet rubbers of course) and building up a new back wheel from a Virago to alter the gearing for acceleration. Did have a number somewhere for him - but failing that try UK directory of enquiries.

Will dig out that number if you want to follow this up and can't get anywhere.

[clarknobb]

I am in UK near Bedford. I am planning to sprint mine (when I can get the carbs spot on) so any info you can find would be a big help.
Cheers Nobby.

[chopper]

nobby,you tried emailing yamaha in amsterdam? they were main european importers and more likely to speak english than the factory

[clarknobb]

chopper Im working on it! Ill keep you posted.