Replace or swap?

Every XJ is a project whether big or small. Tell us about yours.
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Unit562
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Tue Oct 10, 2017 2:25 am

My poor SECA II's engine is toast. The question is, replace with the original engine, or swap with something else? I've tossed around the idea of tossing in a large V-Twin from something off Craigslist.... Would that make a heretic though?
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Casper
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Tue Oct 10, 2017 6:09 am

A few of us would love to see the project of putting another engine in the Seca II frame, but a large Vtwin is a lot of fabrication.

If you've got the tools (or willingness to buy them) and the determination, then go for it!
Men do not quit playing because they grow old; they grow old because they quit playing.

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TwoWheelGeorge
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Tue Oct 10, 2017 9:13 pm

Why not try this....
Rebuild the stock engine, but, make it high performance. Maybe cams, jet kit stage 3 or 7, better exhaust, nice intake.

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Casper
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Wed Oct 11, 2017 9:01 pm

Cams are much easier to find when there is aftermarket support. I have yet to see a drop in cam replacement with taller lobes, let alone anyone who has measured to see if a taller, different duration cam would even work with the piston to valve clearances. You're not going to get a larger valve in the head without a lot of work. You're not going to find a compatible replacement head without a lot of work. You're not going to get enough airflow to justify a bigger bore / longer stroke. Stock intake and exhaust are very, very well tuned from the factory for the airflow through the head and we have only seen marginal improvements if not detriments to the performance due to changes in the intake and exhaust.
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Slartibartfast
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Thu Oct 12, 2017 7:37 am

What about going for something closer to stock but a bit more powerful, say something like an FZR600 lump? liquid cooled and nearly 90bhp (when new) but still a 600 in-line four so maybe less effort required?

Anything is possible, it just depends how much time and money you want to throw at it. I for one would love to see it done though!
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TwoWheelGeorge
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Thu Oct 12, 2017 3:17 pm

Casper wrote:
Wed Oct 11, 2017 9:01 pm
Cams are much easier to find when there is aftermarket support. I have yet to see a drop in cam replacement with taller lobes, let alone anyone who has measured to see if a taller, different duration cam would even work with the piston to valve clearances. You're not going to get a larger valve in the head without a lot of work. You're not going to find a compatible replacement head without a lot of work. You're not going to get enough airflow to justify a bigger bore / longer stroke. Stock intake and exhaust are very, very well tuned from the factory for the airflow through the head and we have only seen marginal improvements if not detriments to the performance due to changes in the intake and exhaust.
Very interesting, because I was planning on looking into doing some of these things over the winter. I am at least planning on using a stage 3 jet kit, k&N airfliter (either the drop in or individuals), and some straight pipe probably. Not worth it?

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Casper
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Fri Oct 13, 2017 11:51 am

TwoWheelGeorge wrote:
Thu Oct 12, 2017 3:17 pm
Casper wrote:
Wed Oct 11, 2017 9:01 pm
Cams are much easier to find when there is aftermarket support. I have yet to see a drop in cam replacement with taller lobes, let alone anyone who has measured to see if a taller, different duration cam would even work with the piston to valve clearances. You're not going to get a larger valve in the head without a lot of work. You're not going to find a compatible replacement head without a lot of work. You're not going to get enough airflow to justify a bigger bore / longer stroke. Stock intake and exhaust are very, very well tuned from the factory for the airflow through the head and we have only seen marginal improvements if not detriments to the performance due to changes in the intake and exhaust.
Very interesting, because I was planning on looking into doing some of these things over the winter. I am at least planning on using a stage 3 jet kit, k&N airfliter (either the drop in or individuals), and some straight pipe probably. Not worth it?
Engine is the low flowing part of the system. There is someone currently porting a head on another forum, but I haven't seen any results yet.

I would love for you to prove me wrong, but don't enter with high expectations without thinking of spending a chunk of change.
Men do not quit playing because they grow old; they grow old because they quit playing.

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TwoWheelGeorge
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Fri Oct 13, 2017 1:49 pm

So, your answer is don't waste your time or your money. Well, at least you'll get a nicer sound with open filtera and straight pipes.
I guess that's an improvement lol

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TonyKZ1
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Fri Oct 13, 2017 2:37 pm

It'd probably run better with the stock airbox and dual exhaust system. As for a nicer sound? I guess it would depend on who's hearing it? ;-)
1997 Yamaha Seca II - mostly stock, Racetech upgraded forks, FZ6R rear shock, Oxford Adventure Style Heated Grips, Barkbusters Blizzard Cold Weather Handguards, a Scottoiler vSystem chain oiler. My Mileage Tracker Page.

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TwoWheelGeorge
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Fri Oct 13, 2017 7:43 pm

Man? You guys are tough critics. So leave it stock? I really respect your opinions because I am totally new to this, and basically playing it by ear. Gonna have think this through lol.

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