Uprated valves, engine refresh, and head skim

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Gollum
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Uprated valves, engine refresh, and head skim

Post by Gollum » Thu Feb 10, 2022 6:32 pm

Hi guys..

Can anyone advise of a supplier of aftermarket performance valves please? I'm refreshing the engine, and skimming the head to raise the compression a bit.

Many thanks in advance

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Tarwetijger
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Re: Uprated valves, engine refresh, and head skim

Post by Tarwetijger » Fri Feb 11, 2022 11:30 am

Some time ago there have been made a batch of bigger valves (edit: 9 years! http://www.trx850.com/phpBB_forum/viewt ... f=6&t=8957 ), I suppose they are rare nowadays.
You could try Pieter Hessels from HPS motoren (Netherlands), see details at: https://www.hpsmotoren.nl/en/
I'm not sure of he still has them. It wont be a bargain anyway.

Cams should be easier, as Kent cams still make these. https://www.kentcams.com/
Pieter from HPS has two versions of cams though, as the Kent website only mention one type "YAM9".

cobbadiggabuddyblooo
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Re: Uprated valves, engine refresh, and head skim

Post by cobbadiggabuddyblooo » Thu Feb 17, 2022 12:27 pm

Don’t skim the head, just remove the centre shim from the MLS head gasket.
Re-use the old gasket, clean off the old viton deal with thinners , remove the centre shim and use the 2 outer spring sheets with a coating of Hylomar blue. ( locating dowels will centre the 2 outer sheets ) Will bump your compression up just shy of 11:1 and makes the motor a little more responsive. Yam-9 cams will give you a little more inlet Duration, 0.3mm more lift and a touch more dynamic compression but run out of puff at 7500rpm like the std cams. You’ll find 80 hp peak but some nice gains in torque. Cheap investment for $500. Add an Ignitech prog ignition , replace the coil leads and push 40+ advance running 98 and find further gains. $750 total and the std trx jetting runs rich so std jetting should work well for a base setting.
You’ll rob Peter to pay Paul if you change header diameter with a loss of velocity down low for 1 or 2 more HP at peak with 50mm outlet cans.
You can re-use the cam cover gasket a number of times too.
I’ve done the head gasket mod to a few trx rebuilt motors and all still going strong. I re-used the MLS gasket a number of times on my trx with 12.5:1 comp motor with no issues too.
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jpe70
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Re: Uprated valves, engine refresh, and head skim

Post by jpe70 » Thu Feb 17, 2022 8:57 pm

cobbadiggabuddyblooo wrote:Don’t skim the head, just remove the centre shim from the MLS head gasket.
Re-use the old gasket, clean off the old viton deal with thinners , remove the centre shim and use the 2 outer spring sheets with a coating of Hylomar blue. ( locating dowels will centre the 2 outer sheets ) Will bump your compression up just shy of 11:1 and makes the motor a little more responsive. Yam-9 cams will give you a little more inlet Duration, 0.3mm more lift and a touch more dynamic compression but run out of puff at 7500rpm like the std cams. You’ll find 80 hp peak but some nice gains in torque. Cheap investment for $500. Add an Ignitech prog ignition , replace the coil leads and push 40+ advance running 98 and find further gains. $750 total and the std trx jetting runs rich so std jetting should work well for a base setting.
You’ll rob Peter to pay Paul if you change header diameter with a loss of velocity down low for 1 or 2 more HP at peak with 50mm outlet cans.
You can re-use the cam cover gasket a number of times too.
I’ve done the head gasket mod to a few trx rebuilt motors and all still going strong. I re-used the MLS gasket a number of times on my trx with 12.5:1 comp motor with no issues too.
What he wrote!

Skim head only if faulty or putting serious money into the engine. Thinner head gasket works a treat. Ignitech with custom advance is fun to tinker with too and will improve the lumpy engine. Exhaust config is basically which way you want to go. Torquey roadbike or peakier track bike.

HPS Motoren will supply you with larger valves and high comp pistons, usually they have things in stock or on fairly short order.

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Re: Uprated valves, engine refresh, and head skim

Post by cobbadiggabuddyblooo » Fri Feb 18, 2022 10:48 am

Was looking at Dyno charts the other day Jan of a friends std TRX motor with Ignitech , Over exhaust and FCR41’s.
2nd chart was after fitting some Penner cams from Huby in Germany. 8HP gains from 4000rpm to 8500rpm
Next stage is port work, oversize valves and 11.5:1 868 Arias pistons so looking forward to seeing the further improvements.
Another mate has a TDM 850 motor in an XTZ with Ignitech and FCR39’s. His next stage he has the other pair of matching Arias pistons but with Kent cams, oversize valves.
Now that would be dynamite on the dirt.. :lol: I’m havin a ball on the dirt roads with my 630 Transalp so could just imagine what the XTZ will be like...
laughter is the best medicine

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