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Taffy

more midrange

5 posts in this topic

i checked all the durations & lift last night & have come to the conclussion that there may be a midrange boost available.

the exhaust cam appears to be very retarded- by as much as 7/8 degrees. i had my wr turned into a wz about a month ago & love the performance improvement. it doesn't jolt forward though when i hit the throttle which is what i want to work on.

the cam topped out at 101/102 degrees btdc & i hope to try the change to around 109/110 this will give i hope a boost in midrange.

each tooth change on the cam is worth 22 1/2

degree's so according to my engine when the timing was retarded one tooth, i went a 1/3 too far. don't forget a 'tooth' means the top & the bottom part.

has anyone pulled the camwheel off the camshaft. i'm not rich enough to ruin this unnecassarily.

the only reason i'm not more excited is because every engine is different. the cam should top out between 100-110 degrees btdc. 100 is for top end & 110 is for torque. i've got a lot of races coming up & don't want to get it wrong so i may hang on. that info on splitting the wheel & cam would be very handy.

i've mailed stroker for details on their two types of cam, if anyone else can get any joy & get some figures please mail me.

Taffy

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Taffy,

You're saying that the stock WR exhaust cam timing peaks at 124 degrees BTDC. Is this an abnormal amount of cam advance under most circumstances? Do other more conservative (i.e. quiet) engine designs use this range of timing?

James

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James

sorry for the late reply but your 4.42pm is after midnight for me. i'd swap any day-just to see the olympics! they start at midnight & i'm going to be knackered by the 16th day.

anybody who can move the timing by one tooth is being very radical with your engine. you normally talk in increments of 1 or 2 degrees which is 1/10th of a tooth.

the exhaust cam doesn't have quite as dramatic results as the inlet cam. the wr timing is kicked out not so much to give the engine more torque as really to soften it-ie no gain. in other words it has been set up to be a YZ & not a wr at all.

the inlet is, at 109 degree's atdc ready for a strong upper end engine. the exhaust cam doesn't match the inlet & if nothing else i think they should be working toward the same type of power curve.

basically if i want to do this experiment i have got to pull my bike off the track & will have to go to my engineer friend who has been with me for 20 years. we'll design some way of using offset (woodruffe) keys & pray i don't drop one down the engine!

the problem is; how many times do you pull a camwheel off before it falls off!

i'll think of something don't worry.

Taffy

[This message has been edited by Taffy (edited 09-16-2000).]

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anyone able to measure the thickness of a YZ base gasket TODAY as i need to know NOW. the WR is .020" (.5mm) let me know ASAP please. ta

Taffy

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anyone able to measure the thickness of a YZ base gasket TODAY as i need to know NOW. the WR is .020" (.5mm) let me know ASAP please. ta

Taffy

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