350x engine rebuild questions

[whiteR]

just need some input my 350x motor. it had rod failure and broke in half destroying the bottom end. the top end wasn't touched . got a used bottom end with good crank . the engine never smoked . while it is apart should I do anything with the top end new valves, seals, springs , retainers, valve job etc..., I have new gasket kit and seal kit plan on putting new clutch kit in also. new piston and rings already done and bore job done, any info would be greatly appreciated.

[Flyingw]

The bottom end is pretty straight forward, Gaskets, seals, clutch plates. Clean and inspect your tranny and crank bearings.

[Flyingw]

As far as the head goes, Never hurts to lap the valves and put new valve stem seals on them. Check your spring free length.

[oscarmayer]

if you have a friend with a tumbler, take the newer bottom end apart and have the trans gears polished up. it will help with strength and shifting a ton!
the rod, honestly, I would call HotRods or CrankWorks and see if they can help with a stronger setup. but a stock rod snapping usually means 1 of 3 things happened. hydrolock (water sucked down the carb when engine was running and caused it to snap the crank), or piston to valve damage due to clearance issues, or debris got into the bottom and the bearings let go binding the crank and poof.

regular maintenance and using good air filters will help a ton. if your not on an MX track, use the stock airbox with the lid. it helps keep dirt and water out of the motor better. Change the oil every 2 months or 4-5 rides. oil is cheap compared to a blown motor.

Good luck sir! O7

[wonderboy]

If you haven't already, be sure to get the service manual since there is important info in there. When putting the top end back together, the cylinder head cover doesn't get a gasket but uses Hondabond instead (per the manual). You need to be tidy when applying the Hondabond, and there are some keep-out zones illustrated in the book. You have to keep the sealant out of these areas to avoid it squeezing into the cam bores which would be bad.

216238

Other advice:
* Since you are rebuilding your clutch, take the time to file the grooves out of the clutch basket. This will let the clutch plates float better and will give smoother clutch action and less drag.

* Use a torque wrench for every fastener. It will take longer, but it will prevent pulling the threads out of the aluminum. I've worked on many motors where the bolts have been overtorqued, which pulls the threads a bit. After a few more assembly / disassembly operations they strip completely.

* Clean mating flanges completely. Don't gouge them with a metal scraper. The easiest way (and a good excuse to buy a tool if you don't have one yet) is a 90 degree air grinder with a scotchbrite pad. Something like this: http://www.harborfreight.com/air-angle-die-grinder-32046.html

* Install paper gaskets without sealant. You can put a light coating of oil on the side cover gaskets if you want to ease disassembly later.