Just about everything is interchangeable across the range, with enough knowledge... However, as you have found out with the RC Valves, for example, a little knowledge can be dangerous! 🤣🤣🤣 The different top-ends do indeed have different ranges of motion on the RC Valves.
Out of curiosity, is the SP motor you have 1990-1996? Are the barrels round?
If it were me, providing the original bottom-end is in good condition, I would probably look at rebuilding the 1988 top-end, and swapping the dry clutch transmission into the 1988 cases. However, the benefit of the SP motor [if it's MC21/28] is that you can still get brand new cranks for them, which you cannot do for the 1988 R2/4J models. (T2Racing do a reproduction centre seal, and the cranks can usually be rebuilt though.)
Regarding your proposed scenarios:
- The TYGA 300 kit is very good these days... it's had 20 years of development! However, it's not "a substantial increase in power", as you put it. What you will get though, is a very noticeable increase in bottom-end and mid-range drive, which carries through to the top-end in quite a linear fashion. You can of course pay extra and have Matt put a tune on it, but really you want tailor made expansion chamber, slightly bigger carbs, and maybe even a different ignition to really make the most of it. It can get extremely expensive.
- Stock bikes (or at least stock appearance, with easily reversible modifications) are worth considerably more than modified bikes, and are increasing in value year-on-year. You can't expect someone to pay for your 300 kit and all the associated mods should you decide to sell it... well, not in my personal experience, anyway, so you're always going to lose money if you go that route. If it's [close to] standard though, it's much more likely to fetch a premium. Of course, you may be lucky and be that one in a thousand who gets luck and is paid back for all the customisation, but it's extremely rare. Modifications are very subjective and personal. I know if I ever sold my MC21, all the HRC parts would come off it and be sold separately, because they add little value to the bike as a whole, but would sell for ££££s separately! (The forks alone sell for £2k these days!😳)
Anyway, that's what I think... I'm sure other's will have a difference of opinion and be along soon.
Please feel free to start a thread on your (re)build sometime, so we can follow along.
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Andy.
NSR-WORLD.COM
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