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Max power with 39mm FCR?

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Hi all, I was just wondering what the HP ceiling of a motor might be with the 39mm FCR carb might be. From reading the 50hp thread, I'm guessing it might be around 48hp, as to get a true 50 it's seems the 41mm is required along with the RHC187 cams. (I'm thinking with 434 bigbore)

Because my kicker has a different crank I only have the Yosh kit as an option if I wanted to run a stroker crank, so I'm weighing up other options.

Many thanks.

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Ok thanks you two. It makes sense that there would be losses after peak, to be honest I'd be very happy with 50hp.

After reading the 450 Yosh kit would make about 50hp, it looked quite attractive, although, I have reservations on the price and the longevity of the 2 ring piston.

I'm betting I could make a 50hp motor cheaper than the Yosh kit costs.

The bike is unlikely to see road use, after having a day on a kart track, I enjoyed it so much, I decided to do a dedicated SM conversion. Offroading was fun, but, ultimately not for me. I always had this in mind as a backup plan, in case I didn't take to the mud.

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That's exactly what I was thinking, since the bike I'm planning to do this to is an E kicker, I have the cams and the carb already, it's done 3705 miles, so I'm pretty confident the bottom end is good, though obviously when I take the top end off I'll inspect it properly.

As for the top end, I'll replace the valves and springs, more than likely with RHC items, I really don't want to be building this motor twice!

Since fitting Hotcams is not going to net me a great improvement I'm intrigued by the 187 cams, given the bike is going to live on the track, what's your thought on running a pair Eddie?

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Cool, thats the displacement, the valve train and the cams sorted. Now I know where I'm going with the motor. I'd really like the motor to hoik the front wheel into the air when it comes on cam! :banana:

This isn't going to happen overnight, got lots of tracktime organised for this season, so going to run the stock motor with just a pipe, got the brakes sorted, re-sprung the shock and fitted an SM front end. I like to do my homework in advance.

I'll be collecting the parts until I have everything I need, then get it all setup on the same dyno I always use, which incidently my SM reads exactly the same for a mildly modded SM as the charts I've seen from your dyno Eddie, so I know when I'm in the right ballpark. My dyno guy is very good, we work together well, which is why I go there.

Thanks gents for your help.

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The parts I need to collect together for the top end are:

RHC in/ex valve kit in standard sizes?

RHC 187 inlet cam, (do you have a price just for the inlet?)

SSW stage 2 spring kit.

Also I take it that since the stock head supports 55hp, porting isn't going to be necessary?

Is that correct? If you're still not shipping to the UK, I may have an address in California I could get them shipped to.

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Cheers Eddie, I had a couple of other questions, but, I can't remember what they were now! :thumbsup: It'll come to me, hopefully.

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If i remember correctly 55 HP with stock head was with very high compression.

That does not change the fact that the stock head supports lots of HP. Above 50.

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Eddie, can you tell what the power difference will be between:

1) Hotcams IN & EX

2) RHC 187 IN & Hotcams EX

3) RHC 187 IN & EX

Setup:

FCR39MX

434 CW BB kit

MRD/SSW

RHC valves

SSW springs

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187's are to much for a 434 unless used on a roadrace course along with a 41mm fcr.

you want hotcams stg 1 for that set up if your looking at off the shelf cams. i have some other custom cam grinds that may work for you as well depending on the type of riding.

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Next year I'll just ride on the track.

I plan to mount this winter CW 434 bb kit and get it as much power as possible.

But with FCR39 - FCR41 is too expensive for me now.

I know that I must have a new RHC valves and SSW springs (18.000km).

But I do not know which cams to use.

Can you tell me more about these cams:

"other custom cam grinds that may work for you as well depending on the type of riding."

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