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Small vlave/big valve head swap ?

Joined Oct 2012
120 Posts | 0+
Right, so just following the logical route to a conclusion here really, and with a view to understanding the possibilities and potential of mods......( I read posts a while back of gen2 heads on gen1 engines...soundz painful ! )
1) - Can the bigger valve heads be supplanted to the early small valve motors....
(as this would seem an easier option to the other question.... )
2) - Can valve seats be inserted in small valve heads and worked to take the 38mm valves ( +guides etc...)

Well, it makes sense to me ! ?? :dunno

TIA
 
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Anything is possible for the right money ....

But I have seen a few posts with people swapping heads , dont forget you would need the matching T/B's as well.
 
Tim, as Kiwi said anything is possible, but the easiest thing to do would be to fit a Gen2 engine (£450 then sell your engine) and swap the stator and flywheel from your engine + a couple of other bit and then the exhaust you bought will fit straight on.

Mark
 
Tim, as Kiwi said anything is possible, but the easiest thing to do would be to fit a Gen2 engine (£450 then sell your engine) and swap the stator and flywheel from your engine + a couple of other bit and then the exhaust you bought will fit straight on.

Mark

Ok, reading between the lines then, "no, the heads are not a fit". - and implied is that the valves (stems) guides, seals and possibly chain drive etc are all redesigned by Aprilia ( Edit rotax ) to get the bigger valves....

Just to put you in the picture..I dont know what my engine is beyond Gen 1.....not without taking the heads off and measuring the valves I guess !

Mark, does the big bore require valves @ 38mm. ?
 
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Anything is possible for the right money ....

But I have seen a few posts with people swapping heads , dont forget you would need the matching T/B's as well.

So , you have implied that all bigger valve, Gen 1 engines have 57mm TB,s.. ie 99-00 has small valve , 51mm TB,s, & 01-03 ( 38mm valves) run 57mm TB,s.... cos this MIGHT be the answer that has eluded me as to the easy way to know what engine you got !
 
Tim, there is a date manufactured stamp on the barrels, looks like a sun dial. Hard to see with the engine in situ. though.

01 models run 51mm TB's as standard. All Gen 2's run 57mm.

Valve sizes through the years.....

.......... Inlet Exhaust
1998-99 36 31
2000 36 31
2001-02 38 31
2003 38 31
2004-05 38 31
2006 on 38 33


Some Yank bikes had smaller valves 2001-03.

As Mark says, converting to 06 onwards heads is possible but expensive & requires machining. Had a Danish chap buy a pair of late heads from me, there's a thread somewhere on here about what he needed to do.
Far cheaper to swap in an 06 onwards engine. Just so happens I have a 7000 mile, prime example sitting on the garage floor...

HTH

:thumbup
 
Yo....thanks for replying. I feel like I am banging my head against a brick wall !!
Alls I want to know is why gen 1 heads are not interchangeable with gen 1 engines.....!?
I'll have peep on the barrels ....


Eureka..... 01.
 
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Yo....thanks for replying. I feel like I am banging my head against a brick wall !!
Alls I want to know is why gen 1 heads are not interchangeable with gen 1 engines.....!?
I'll have peep on the barrels ....

yes you can fit big valve heads on a small valve engine.... no probs!

youll struggle to fit Gen 2 heads on but it is poss!

and you dont need big valve heads on our bore kits, but it helps!

valve sizes really will help an engine respond to tuning, to a certain degree!

hope this helps dude!

Griff
 
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