cam timings holy grail?

Dale

just about to have a look at the cam timing again because this time when i pulled the head off the cam was ******** one tooth visibly!

i had taken the clutch unit off and re-aligned it according to the oft-touted diagram that we can all find.

on the one hand i'm trying to do cam timing with a pair of dots that don't line up and on the other i'm looking at a pair of lobes to see how symmetrical they look!

not exactly science.

i get the feeling that i need to start all over again here. those bloody lobes were symmetrical two weeks ago!

not so much asking for a definitive answer as to say did you in your early berg career have to sit down and redefine how you would time your cams so as to get it right everytime and avoid these mistakes?

one other thing: if you have the lobe centres for the '01' and '53' cam i'd appreciate it as well. whilst i have your graphs i believe that this is a statistic i have yet to see.

regards

Taffy

cheers dale

i've checked and it would appear that although i thought the 2 and 1 dots were aligned there was one more tooth that would have meade the result even more precise. that's twice in a month and i'm getting sloppy.

i have PM'd you and hope i can get one more piece of info from you. thanks for the help.

regards

Taffy

dale

well i read your message at tea time saturday and 30 minutes earlier and i'd have sat on a stool for an hour gawping at the three gears in question. but i'll sit here and think about it anyway.

first of all i hope a lot of the lads read this because it's bloody important and is deserving of a headline of it's own: when i've done the valve timing in the past i have put the engine back together after say doing the clutch.

only one of the double dots lines up with the single dot gear and in turn are both in line with the centre point of their two gears. THIS IS NOT AS PER DIAGRAM AND NEVER HAS BEEN.

i've NEVER had the two dots dissected by the one!! so last night i decided to try and get everything right and lined the dots on the two gears, fitted the cam and found it to be the very half tooth out that you're on about. today i have lengthened the slot in the camwheel to ****** the cam timing THEN i come in just after i've done it and read your message.

this is really annoying!!!

just for you though dale i will mention that i've got the timing to 109d ATDC on the inlet ( an advance of three degrees). i did it by setting the side gears so that the single dot dissected the double and all in line with the gear centres.

advancing the cam (the correct timing brought me to a point between two teeth) and then ******** the timing using the slot. can't go any further as the machined hole in the gear is now only 1.1mm wide at the narrowest point!

something that i may retime another day when i pull a stool up, have a look see, eat a sandwich and chew on it as they say!

i figure that the tensioner has a couple of clicks in it yet and the head will be re-torqued after the first ride. then of course we could always talk of the camchain stretching... but we won't!

started first time and really does run sweetly in the shed.

having checked the cam timing the inlet 's timing is way different to the exhaust at 112d inlet and 122d exhaust. if however the timing is changed to 117d (the timing of a '55' cam) inlet, the exhaust is also 117d making me think that the cam was designed essentially as a '55' and not a '53' cam.

anyone tried the two on a dyno or back to back in testing?

Taffy

dale

went for a MX practice yesterday and had my valve bounce return?

today i have pulled the head off and re-checked the timing and as i suspected the inlet is at it's peak from 100 to 126 degrees. taking the middle of that i make the timing to be 113 degrees and therefore only 1 degree out for a 53 cam.

have i got this formula for checking the valve timing right please?

anyway i have nice shiny half moons in the exhaust valve cut-outs. the valves didn't let any paraffin through when laid on the bench so i'm figuring that they'll be ok to go again.

i put some plasticine in the exhaust pockets and checked the v to p and it didn't even register on the plasticine again as it didn't when i set this up. so it's over 5mm and i therefore have valve bounce.

it was doing it very, very easily. any excuse and it would give 'the raucious roar'.

whilst i haven't put your spacers in yet under the valve springs, do you think that this will make such a difference? after all they are the tiniest of the husaberg valves at 27mm?

cheers

Taffy

hi dale

i've played with it and would like to run the figures by you. i tried the 1mm of lift but it wasn't making your maths wok too well!

if i did 1mm of lift, i measured at the base of the rocker arm just infront of the tappet nut, then the inlet opened after TDC so i went to .5mm of lift and had this:
opening 0.5mm of lift =1 degree BTDC
closing 0.5mm of lift = 43 degrees ABDC

total opening 224 degrees
half = 112
less 1 degree = 111 degrees 'intake lobe centre'

i'm happy with this as it's a fairly tight lash-up but not the real thing. doing the valve timing on strip down 'my way' the timing had slipped from the 109 degrees i'd set it to 113 degrees, a rough but accurate guesstimate!!! however my way was the wrong way.

i've changed the way i used the camchain tensioner this time and all i did was pull the spring out the back but used the CCT how it was stripped. so allowing 2 degrees! i will do one last check with everything bonded and cleaned and all screws in etc.

in your last sentance your timing figures would add up to 244 degrees and half is 122 less the 10 degrees opening BTDC = the 112 we're looking for!

the difference between the way you do it and the way i had presumed was about 12 degrees but due to there being no more play in the camwheel slot i ******** the camwheel a tooth, advanced a tooth down at the timing gear to clutch and then played with the slot again. this barely moved thus the 12 degrees being acheived using the gears and sprockets virtually.

the next thing is that although you told me previously that my kissed valve seats had ressessed the valves .75mm i didn't find out what value you use?

the exhaust valve stem tip sits 39.5mm above the aluminium surface upon which the steel washers and valve springs sit. is this your measurement? 1.320" = 33.4mm? is this the gap twixt underside of collar down to steel washer. the height allocated to the spring?

i measured the space for the spring and it works out at 34.1mm which is .7mm more than the figure you gave me and ties up neatly!

thanks for this.

Taffy

yes it does help dale thanks. i've got the handle on that now.

Taffy

dale

i gave up in the end! i kept getting the duration of 244 degrees off of initial DTI movement and stop. when i set it like this the two cam lobs were symmetrical and it was too good a chance to miss!

sadly i didn't have the battery fully wound up and didn't get it running in time to race today with my favourite club. i didn't know for certain that it was the battery so i didn't ask anyone here for a bump! now i know it was, i wish i'd knocked anyone up i could find! however i did go for a test ride and the cam is lovely! pulls hard through the middle and is most noticeable at the change in each gear as your head gives a little extra nod backwards.

valve timing at the end was as follows:
zero tappet clearance (1mm lift)
IO TDC
IC 30 ABDC
=210d duration
=105d CLC

zero tappet clearance, measured as needle moves:
IO 11d BTDC
IC 54 ABDC
= 245
122.5 - 11 = 111.5d CLC

thanks for the figures. will have to try one of yours one of these days!

regards

Taffy