- Joined
- Nov 20, 2001
- Messages
- 17,028
- Location
- Ely, England
I recently commissioned someone known for flowing and testing heads to have a look at mine.
I sent in three heads.
head 1 was a bog standard 35/30 head as fitted to all bikes 2004-2008
head 2 was a bog stock 37/30 head as fitted to all 470/501/550/650s from 2001-2004.
head 3 was a ported head. 37/32 with the same entry as original but heavily ported down from there. valve guides still 100% in there BTW!
the 35/30 flowed marginally better than the others up to 2mm. and the important bit to note is that the show was over at 9mm. absolutely no gain at 10mm opening. the reason it is better at >2mm is because it is smaller! 35 beats 37.
the standard 37/30 was poorer than the above head to 2mm and then after that was better just up to 10mm where it ran out of breath.
the ported head flowed exactly the same as the above to 2mm and then took over completely with 10%-15% better flow all the way to 11mm. awesome! and before you mention it, this is just inlets, the exhaust has nowt to do with it here.
the above three were measured through the keihin carb and use of the inlet rubbers necassary.
the next test was with the lectron carb but that was only attempted on the 3rd head and gave better flow figures at all revs by 5% but died at 11mm as well.
all these tests had been done with the OEM 37s fitted and no mods to valve seat width. so neither were any changes made to a set of valves from the USA. I had the backs of the valves altered to three different designs and the results were dramatic. One particular design the flo - engineer described as 'a complete aberation!'.
the result was a 5% better flow yet again on all previous figures at anything above 1mm (again!) and the figures were for some reason poorer at 10 and 11mm by 2%. however, because it was a bit of a hack job we sussed that the backs of the valve near the stem could be sloped down some more and probably that would go as well and be back to 100%.
i wish he had checked for weaknesses but he seems to have forgotten to do this. then again - he is 80! the valves are now for sale on e-bay and DO work. they flo better where it matters and despite being thicker section still weigh 5gms less than OEM and aren't expected to tulip. I have yet to re-value the time and effort spent on them but for now they are for sale for £50 each instead of the factories £95 each.
I have also had some machined down to 36, 36.5mm and have just 2 left at 37.75mm. will restock when needed.
the 36s can fit a later husabergs (the 35/30s) but i didn't machine a set of seats to test them but look, the 35s and the 37s have the same profiles as do the ports so you know....2 + 2 etcetra. Katooms as wel would love them i guess. :cuss: :cuss: :cuss:
I could have done a load for huskies as well but...oh well! :evil: :evil: :evil: sh happens.
i can't give anymore accurate figures than these because i've lost the fact sheets somewhere. you know how it is... :twisted: :twisted: :twisted:
regards
Taffy
I sent in three heads.
head 1 was a bog standard 35/30 head as fitted to all bikes 2004-2008
head 2 was a bog stock 37/30 head as fitted to all 470/501/550/650s from 2001-2004.
head 3 was a ported head. 37/32 with the same entry as original but heavily ported down from there. valve guides still 100% in there BTW!
the 35/30 flowed marginally better than the others up to 2mm. and the important bit to note is that the show was over at 9mm. absolutely no gain at 10mm opening. the reason it is better at >2mm is because it is smaller! 35 beats 37.
the standard 37/30 was poorer than the above head to 2mm and then after that was better just up to 10mm where it ran out of breath.
the ported head flowed exactly the same as the above to 2mm and then took over completely with 10%-15% better flow all the way to 11mm. awesome! and before you mention it, this is just inlets, the exhaust has nowt to do with it here.
the above three were measured through the keihin carb and use of the inlet rubbers necassary.
the next test was with the lectron carb but that was only attempted on the 3rd head and gave better flow figures at all revs by 5% but died at 11mm as well.
all these tests had been done with the OEM 37s fitted and no mods to valve seat width. so neither were any changes made to a set of valves from the USA. I had the backs of the valves altered to three different designs and the results were dramatic. One particular design the flo - engineer described as 'a complete aberation!'.
the result was a 5% better flow yet again on all previous figures at anything above 1mm (again!) and the figures were for some reason poorer at 10 and 11mm by 2%. however, because it was a bit of a hack job we sussed that the backs of the valve near the stem could be sloped down some more and probably that would go as well and be back to 100%.
i wish he had checked for weaknesses but he seems to have forgotten to do this. then again - he is 80! the valves are now for sale on e-bay and DO work. they flo better where it matters and despite being thicker section still weigh 5gms less than OEM and aren't expected to tulip. I have yet to re-value the time and effort spent on them but for now they are for sale for £50 each instead of the factories £95 each.
I have also had some machined down to 36, 36.5mm and have just 2 left at 37.75mm. will restock when needed.
the 36s can fit a later husabergs (the 35/30s) but i didn't machine a set of seats to test them but look, the 35s and the 37s have the same profiles as do the ports so you know....2 + 2 etcetra. Katooms as wel would love them i guess. :cuss: :cuss: :cuss:
I could have done a load for huskies as well but...oh well! :evil: :evil: :evil: sh happens.
i can't give anymore accurate figures than these because i've lost the fact sheets somewhere. you know how it is... :twisted: :twisted: :twisted:
regards
Taffy
