Currently the engine has about 30,000 miles on it and one of the main reasons I want to do this is the bike is a bit hard to start and a very smokey until it warms up, so if the rings need to be done I might as well just go for the big bore kit.
I'm wondering if there is anything that should definitely be replaced/looked at as I have the top end tore down?
I don't want to split the cases so that leaves the cam chain tensioner out of the equation but should I still replace the cam chain with a split link type one?
Any oil seals/valves or anything that have to be replaced?
How do I measure/check valve guides and seals for wear once I have it apart?
Any ideas if I'll have to re-jet afterwards? (Standard intake and exhaust)
I am a huge fan of the 466 kit. It completely transforms the engine on these bikes. That being said, your smoking problem might not be ring related. It could be from hardened valve seals, worn out valves/guides or a leaking head gasket. You should really start diagnostics with the engine as it is before getting into repairs. I recommend starting with a compression test and possibly a leak down test. I believe the procedures are written up in the FAQ. The most typical reasons for burning oil is from the head gasket or valve guide seals leaking. Those issue can be fixed for the cost of a new gasket kit.
You can check to see if the valve guide tensioner is working correctly by pulling the valve cover off, loosening the lock screw on the front of the engine for the tensioner and pressing down on the rear most tensioner. If it feels spring and moves easily, then the horseshoe is fine.
I pulled a cam chain off that had 40,000 miles on it and it had no noticeable stretch when compared to a brand new DID cam chain. That was for a 350F, but it is identical to the 400F setup. That won't always be the case, especially if your chain has been allowed to come loose, but I'm not sure how to check chain stretch with the chain in situ. Your chain guides might be worn though. Before shelling out the big bucks for new chain tensioners, I'd recommend finding someone with some spares. I definitely have spares in near perfect condition (low cost), as well as brand new items from DSS. I'd sell you either, but the DSS repro units are costly. $110 for the set I think.
Regarding wear checks, you should get a manual and start from there. The leakdown test will give you a good idea if your valves are leaking, but valve wear is more difficult to measure without actually disassembling the head.
You won't need to rejet afterwards if the bike is stock. Even with the big bore kit and stock everything else, you might stick with the same jets, or possibly decrease your mains (higher pressure drop due to higher flow rate resulting from the big bore kit will create a higher fuel flow rate through the carb circuits, which may result in a rich mixture). Stock mains are 78 or 80. If you go down, then go to 75/78 respective of which stock jets you have. I wouldn't bother with that until you have the bike running though. As a reference, a 466 kitted bike with bored out carbs and stock intake/exhaust will need to raise the main jets from 78 to 80 (or similar), to get the fueling right. The bored out carbs will offset the higher pressure drop from the big bore kit, which is why I think you'd be just about right with the stock jetting.
If you pull the engine apart, then pull the jugs off too and replace the ring gaskets around the cylinders as well as the cylinder base gasket.
If you decide to bore out the engine, the make sure you have a machinist who can handle the bores on these blocks. I know of one shop in Petaluma, CA that can do it, but I don't know any other shops in my area that can. I'm sure others can chime in on other shops that can bore your cylinders.
Regards,
Camelman
