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Post by andy on Apr 26, 2007 10:34:05 GMT -5
hi to all worldwide, has anybody tried experimenting with velocity stacks? if so any better than K&N filters?my slight problem is although me sr500 goes well it will not achieve top end as well as ithink it should,plenty of grunt midrange but struggles 80 mph ish, i'm running a 34mm mikuni,freeflow foamtype filter,bsa goldstar straight thro' muffler.hard to tell whether its not getting the juice [tho i have messed with bigger main jets to no real advantage]or is it a breathing problem,thought of trying a different type needle,could do with some advice!oh yeah the compression shows fine on the tester.thanks.
andy
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Post by hopwheels on Apr 26, 2007 13:21:23 GMT -5
I think jumping up to a 36mm carby will make a world of difference is getting more outta your bike. 38mm even better.
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Post by aero on Apr 26, 2007 14:27:22 GMT -5
I have a an idea that a 36 mm carb is about the limit a SR in road trim will take. Going bigger is pointless until the mill can process the increase in supply. Which it won't be able to. When I used to mess about with minis, an 1 1/2" carb gave much better results then a 1 3/4" carb on the road. OK maybe the top end was not as good, but way more fun on the back lanes as the engine responded much quicker. Airfilters; what you want is ram stacks with a 1/4" radius, inside a nice volumous filter housing with plenty of space between the stack's opening and the backwall of the filter housing.  A circular K & N element with a decent thickness, clamped between two sheets of alloy would do it. |
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Post by colinjay on Apr 26, 2007 17:38:58 GMT -5
HI,
I agree with Aero, unless the engine has been worked on, ie. hot cam, flow work to the head and a hi comp piston, a 38mm carbie would be overside and give no more topend performance. A 38mm on a std engine usually results in a slight reduction of lower end and midrange performance, which I suppose could make the bike "feel" as if it has more topend!
For a stock engine a 36mm works well with a big K&N filter (or a modified airbox with a K&N element in it) and a free flowing exhaust.
CJ
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Post by colinjay on Apr 26, 2007 17:50:38 GMT -5
HI,
I agree with Aero, unless the engine has been worked on, ie. hot cam, flow work to the head and a hi comp piston, a 38mm carbie would be overside and give no more topend performance. A 38mm on a std engine usually results in a slight reduction of lower end and midrange performance, which I suppose could make the bike "feel" as if it has more topend!
For a stock engine a 36mm works well with a big K&N filter (or a modified airbox with a K&N element in it) and a free flowing exhaust.
I have an old article from CYCLE magazine in 1978, where the dyno tested a SR with various carbie, and exhaust conbinations. I will try and reduce the size of the scanned pages down to a managable size on the weekend and post them here on Monday.
CJ
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Post by andy on Apr 27, 2007 10:49:05 GMT -5
thanks colin,that would be a great help,i would be very interested to see the improvements on the dyno rather than shooting in the dark,i've got a gut feeling my air filter has not got a big enough volume and restricts more at topend of the revs,its one of those foamtype filters which is approx 3" o.d x 3" long,if that throws any light on the matter.
regards,
andy
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Post by colinjay on Apr 29, 2007 23:21:27 GMT -5
Andy ond others,
The article was by Gordon Jennings in the July 1978 edition of CYCLE magazine, I have had trouble trying to upload the scanned pages, but, 1f you want to PM your email adress to me, I will email copies of all 9 magazine pages to you.
CJ
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