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2003 Yamaha Big Bear 400 cam


Vertigo
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Couple of questions-picked up a too cheap to refuse 2003 YFM400 4X4, turns out has a wiped cam, and cam guides.
Obviously in course of redoing top end, i need a new camshaft. Any suggestions/sources? I'm leery of teh "Niche" brand-unless someone can confirm they are suitable.
I also see a "Caltric" brand available on line-but nobody posts actual lift/duration specs on their product. I don't need a crazy race cam, but a bit more torque is never a bad thing imho.

I sure don't feel like paying oem usury prices-options include preowned-which may not be a bad way to go.
Any thoughts/suggestions/experience? Thanks in advance.

Oh, yeah, been searching for the manual for my OIL COOLED beast. I downloaded one, its for the water cooled submodel.

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  • Ajmboy changed the title to 2003 Yamaha Big Bear 400 cam
Dream Car Giveaway

Hey vertigo welcome to Quadcrazy, I picked up a bayou 400, same deal great price not so great head/cam. Journals were wiped out and the cam was burnt up. I contiplated a new cam and reworking the head etc but would up finding a used head assembly from a good motor on eBay for a good price. Glad I went this route. The bike runs like new and it’s all oem parts back on the bike. 

Good luck. 

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Thanks frank, i think I located a 350 BB, not certain of year. Apparently they used the same valve train as the 400 (although the head is different). I've already obtained new rockers,  de-burred and cleaned valve pocket casting lines, stellite seat ridges etc from the intake, and checked  the valves and head. How much should the head be cut to raise compression, a half point or so?
Was hoping to hear from someone who used the Niche cam, "more power, hurrrhuRRR HURRR!" and all, to get some input on output.

I'm thinking i need to clean crankcase really well, any tips? Also, need to examine the oiling system to make sure it wont contribute to early demise of replacement.

Appreciate your comment AJM. Improperly hardened cams can wear fast-and reviews do not seem to reflect well on other Niche products (cylinder kits), although I have not yet read a single camshaft review. I just don't trust the chinese mojo on scrap iron we shipped 'em...is Namura a more reputable piston? Any tips for a 9-9.5:1 piston? I've not found anything but stock 8.6, or full race (which i wont do-this is work beast, not toy).

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Can synthetic motor oil be used with this type wetclutch? Have read conflicting info online.
Also wondering how to clean the crankcase, often I've filled crankcase with kerosene, let sit few days, then cranked engine with starter, finally draining the sludge and using compressed air to blow out and dry bottom end. Dont want to do this if the clutchpaks might be damaged.

I've rebuilt many aircooled opposed fours, as well just about every type of car/truck engine, and have always used synthetic engine oils with great results, some running well over 200,000 miles, one over 300k. After performing cam break in with conventional oil, drained after 30 minutes, refill conventional run a hundred miles, drained. I then switched to synthetic and operated normally, doing a oil change at 1000 miles before adopting a ten thousand mile interval, using the highest-efficiency (smallest particle rating) filter available.

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