Project Motor Swap

[FJ1200W]

There is an absolute mechanical limiting factor (excluding component failure) - valve bounce, and a practical mechanical limiting factor - piston speed.
For a road bike, such as he's building, I took it to be the latter.
Noel

Exactly, it's going in a road bike, "practical".

I just don't want to spit out a shim.

The V&H Powerpak I was considering using has a custom chip with redlines that seem too high for shim over bucket.

What is the maximum "safe" RPM with aftermarket springs?

In regards to the discussions of limiting factors, the starter/alternator drive concerned me, then I started thinking about the supercharged H2 using something somewhat similar to drive the blower......

[Pat Conlon]

Steve, I would go *nowhere near* those ^^^ RPM limits with oem hardware.   

Spitting out a shim with a stock FJ cam profile would not worry me.
Drag racers using high lift cams with steep ramps, yea, I could see that happening.

Consider the FJ engine's durability with Legend and Thunder Roadster racers. These guys race all weekend in multiple heats going around at WFO....night after night....do they spit shims?

I am not a racer, but I know a few on this forum....in fact, I happen to know a guy who was a National Champion.

Pretty cool huh?

Pat

[JMR]

Steve, I would go *nowhere near* those ^^^ RPM limits with oem hardware.  

Spitting out a shim with a stock FJ cam profile would not worry me.
Drag racers using high lift cams with steep ramps, yea, I could see that happening.

Consider the FJ engine's durability with Legend and Thunder Roadster racers. These guys race all weekend in multiple heats going around at WFO....night after night....do they spit shims?

I am not a racer, but I know a few on this forum....in fact, I happen to know a guy who was a National Champion.

Pretty cool huh?

Pat

Yeah....I agree that's a bit to high. Limiting factor for making power is generally cam lift/duration and valve size....you can only get so much air in there no matter how hard you spin it. Honda proved that spinning engines to over 20,000 RPM's.
And then there are the trade offs with cam lift and duration......you need the mechanical ability to control those components too. Everything is a compromise.....just like life

[FJ1200W]

It sounds like there will not be any issues or concerns going back to the stock setup, with the stiffer springs and mild cam, 10,500 would probably be the most, have to wait and see what the dyno shows.

I'm chomping at the bit but have to do a car repair 1st and weather has been bad. The garage is setup for motorcycles, not cars.

I did remove the buckets and shims. Was going to pull the valves but caught myself - no hurry, get the car behind me......

[fj1289]

Well, the most practical answer - a well prepped FJ engine will hold together at higher RPMs than cams and heads are likely to make power at unless you do extensive development on those parts.   So, find out where it really makes power and set it a little past there!

Another way to look at this - the Hayabusa uses similar engine dimensions to the FJ - 1st gens are 81mm bore x 63 mm stroke, 2nd gens got a 2mm longer stroke at 63 mm.  Their stock redlines are 11,000.  And a lot of folks will up the redline when they do cams and head work on a stock bottom end to 12,000 or 12,500.   So I don't think max piston speed is the practical limit.   

I had the drag bike set up for a while at 11,000 shift point.  It had enough cam, port, carb, and displacement to still be pulling hard up there.  On the land speed engines with the milder cams and nitrous, the shift points have been 9,500 but setting the limiter around 10,300 - 10,500 to allow some over rev if needed at the top of the run.  The land speed engines have both been stock shim over bucket with mild cams and performance valve springs.  No problem with spitting shims - even with the large nitrous "pops" in the exhaust on the shifts.   

[fj1289]

Also talked at length with Randy on the spitting shims thing.  I think with good valve springs and mild cams, it is not an issue for the FJ.  I THINK (no personal experience to back this up though) where the risk would come would be large cam lifts that put the lobe much further to the edge of the shim AND get into a valve float incident.  I don't think one OR the other will get you there - I think it would take BOTH and a little bad luck. 

I'd like the hear from someone that has seen shim issues on an FJ engine. 

[FJ1200W]

Well, the most practical answer - a well prepped FJ engine will hold together at higher RPMs than cams and heads are likely to make power at unless you do extensive development on those parts.   So, find out where it really makes power and set it a little past there!

Another way to look at this - the Hayabusa uses similar engine dimensions to the FJ - 1st gens are 81mm bore x 63 mm stroke, 2nd gens got a 2mm longer stroke at 63 mm.  Their stock redlines are 11,000.  And a lot of folks will up the redline when they do cams and head work on a stock bottom end to 12,000 or 12,500.   So I don't think max piston speed is the practical limit.   

I had the drag bike set up for a while at 11,000 shift point.  It had enough cam, port, carb, and displacement to still be pulling hard up there.  On the land speed engines with the milder cams and nitrous, the shift points have been 9,500 but setting the limiter around 10,300 - 10,500 to allow some over rev if needed at the top of the run.  The land speed engines have both been stock shim over bucket with mild cams and performance valve springs.  No problem with spitting shims - even with the large nitrous "pops" in the exhaust on the shifts.   

Useful information, thank you.

As long as the cams I have are marked correctly, there should be no problems as long as I stay within a reasonable max RPM.

I'll always remember the 1st time I saw the intake ports on a 'Busa (or any number of newer bikes/engines). There is no way our "old school" intake ports would even flow like those, and that is another reason for me to not try and build a ultra-high rev'ing engine.

As long as I can keep the Harley's beat, I'll be happy.

And that's getting harder all the time.....

[FJ1200W]

A text message with picture came last night from the machinist and I put the figures into a spreadsheet.

[FJ1200W]

I was able to finish the main project ahead of this one over the weekend.

Looking forward to splitting that cases, inspecting, replacing whatever needs attention and reassembling the who enchilada for springtime fun!

[Indiana jones]

That's good info Rey the shim over bucket config.
I should be good with a Yoshi stage 1 cam then.

[JMR]

That's good info Rey the shim over bucket config.
I should be good with a Yoshi stage 1 cam then.

I ran shim over bucket with Yosh stage 1 cams for years with no problems. Dyno runs, limiter hits etc. One of the big advantages of shim on bottom is the shims weigh much less especially if you use the 9.5mm retainers.

[FJ1200W]

I needed to hold the clutch hub and thank goodness I had kept a set of old burn't metal clutch plates.
And a broken bolt cutter, which I used on of the handles for this tool.
I put the old clutch plates on a board. Then I screwed them in place to assure alignment.
Next I used a large C-Clamp to securely hold it all together and to my workbench.
Then I drilled the holes, installed bolts, spacers and washers, and it worked very well.
Once I get feeling better I'll get those cases split.

[FJ1200W]

Perfect time to make time to split those cases -

[FJ1200W]

Time to check and see what parts I have and what I'll need. Hopefully suppliers are shipping..... And the delivery people, delivering.

[FJ1200W]

See any concerns?