seat recession

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I suspect the failure is due to the hard use they see in my bike.

Hi Jim, welcome back. Can you expound a bit on what you mean when you say “hard use in my bike” as that can mean so many things (sustained high rpm, sustained higher than typical engine/combustion/exhaust temperatures, etc).
 
From what I recall about Jim’s ‘trips’ they’re text book valve seat killers!
 
The solution I found for valve seat recession is TUNGSTEN CARBIDE seats by TUCKER. Ex seats have a Rockwell hardness of 46-52. Thats harder than the FA seats, the Kibblewhite seats and the Nickel Iron seats mentioned in this thread. Intake seats are a bit softer at 40 -45 hard. I have had no problems whatsoever with these seats after 50,000 miles on unleaded fuel. Neither have I seen any seat recession problem with the non-symmetrical cam profiles I use.

Tuckers phone number is 800.362.7321 Note that their standard fractional sizes actually measure .005" larger than the fraction. You'll probable have to order in custom sizes (see sizing below).


seat recession


Custom order for stock seat replacements:

Stock EX seat is .250” tall, seat recess is 1.5 (use 1.507 OD seat – custom OD). ID is approx 1.185 x .159” wall, ask for 1/32 wide seat mating.

Stock IN seat is .250” tall, seat OD approx 1.557”. ID tapers 1.312” to 1.4” x .128” wall, ask for 1/32 wide seat mating.

Use .007" interference fit into valve seat recess. Cut seats with New Way carbide valve seat cutters.

You can use high quality harder seats or softer seats with a shorter lifespan - the choice is yours.
 
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Hi Jim, welcome back. Can you expound a bit on what you mean when you say “hard use in my bike” as that can mean so many things (sustained high rpm, sustained higher than typical engine/combustion/exhaust temperatures, etc).

How about yes to all of the above.
 
Has anyone else with a FA head measured yet to see if clearances are closing up, will do mine tomorrow.
 
No change in mine since last autumn (fall).

Does the fact it hasn’t run since then matter...?
 
Been racing with FA #101 since 2015 and noticed no undue seat recession (gaps haven't closed!) Motor has revved mainly to 7K regularly, occasionally to 8K.
 
I have found this post interesting reading and couldn't help but wonder to about the height of my tappet adjusters in relation to the rocker arm on the exhaust valves. Could it be assumed that here I have receading seats. It is an RH4 Head, bog Standard really and I don't give it a hard time.

seat recession
 
Been racing with FA #101 since 2015 and noticed no undue seat recession (gaps haven't closed!) Motor has revved mainly to 7K regularly, occasionally to 8K.

I would assume you are running leaded fuel, so recession would not be a problem.
 
Here in Germany you can't get leaded any more and it has been like that for several years now. I run unleaded 95 Octane.
 
Here in Germany you can't get leaded any more and it has been like that for several years now. I run unleaded 95 Octane.

You can't buy leaded fuel here for the street either.
But you can go to the race fuel place and buy it in a can. Leaded, with preservatives means it keeps for years without going bad. Also quite pricey.
I am close to the end of the 55 gallon barrel of VP I keep in my storage shed for the dirt bikes, chainsaws, lawn mowers and other small engines. Jim
 
I have found this post interesting reading and couldn't help but wonder to about the height of my tappet adjusters in relation to the rocker arm on the exhaust valves. Could it be assumed that here I have receading seats. It is an RH4 Head, bog Standard really and I don't give it a hard time.

View attachment 10212

It's possible, but hard to say for sure. But if your compression/leakdown is good I wouldn't be worried about it. If they do start leaking you may have to have seats installed with the valve job.

I replace a lot of seats, either because they are recessed or worn out or because someone has been at them with an automotive type valve seat grinder and got carried away. Jim
 
Jim, do you remember if you replaced the seats in FA head #010 , its the one I am using on the race bike that came from you when we did the head for SBR cases trade.
Regards MIke
 
Jim, do you remember if you replaced the seats in FA head #010 , its the one I am using on the race bike that came from you when we did the head for SBR cases trade.
Regards MIke

I don't believe I did. But they should be fine with leaded race fuel, And quite a bit of racing even with unleaded. Jim

After thinking about it.
I may have. If the exhaust valves are 1mm undersized, then I did new exhaust seats. I have done a few like that.
 
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Thanks Jim, this head has 1.5 mm larger intakes so you probably did . Ill check my flow data as the diameter of each Vv is in those specs.
Regards Mike
 
I would assume you are running leaded fuel, so recession would not be a problem.


No Jim, I have never used leaded fuel! Nor any additives. Just pump 98 in UK or France. Compression around 10.5, maybe a little less.

I am not saying there is no recesssion, no untoward recession. I expect a little with high lift cam and race springs. But as you know, the cam in this valve train has taken a hammering!

Steve
 
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