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Truck Yea
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Discussion Starter · #1 · (Edited)
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Some of you may recall that last year I went to Glamis. I got all of 10 mins or ride time and the valves met the piston and that was the end of a 4k Athena 490 build I did. We only reused the cam tower and just saved all the parts in a box in disgust since it tore up the cases and through the motor. As she sits now its a custom done 12.5:1 98mm piston (thank you Matt @ AZ Quad parts!) 470 cylinder by Advanced Machining in Mt. Carmel PA, web cam, race port, steel ferrera +1 valves all the way around, 43mm carb, outwears box lid kit, houser +1 arms, elka 3 legacy fronts, and GT Thunder MX setup in the rear with stock shock.

I tore it down the other day b/c the frame has seen better days and there is a ton of stuff that needs attention. Im again building it up to be a desert/xc quad as I ride in the local sand pits and trails and its like a desert here-all sand. Maybe Glamis again one day but meh been there done that and its fun but it looses its allure after you go a few times.

So far I had one mishap. My old houser +1 arms use a unique aluminum bushing system that they no longer use. Its a AL bushing, with needle bearings thats held in the upper arms with a pinch bolts. I tried to change the bearings but galvanic corrosion-they are a part of the bushing. Houser doesnt make them anymore, BUT I gotta hand it to Alexa at houser-she found me the old supplier whom was more than happy to get me a set. Better than buying new arms. But i still sorta want the arched style arms

my build in many ways was inspired by dirt firsts old school build » Honda TRX450R Race Quad Build Dirt First Racing

Anyways game plan thus far:
-new CRF450 clutch. I think I might go back to stock springs as the feel with my tokyo mod springs is pretty hard. Right now my buddy and I put a CRF500 clutch in there, but I feel as though the plates are to thick causing little play in the clutch setup. its on/off lol and if your not used to it you stall A LOT
-Glann tie rod end kit. this replaces the stock nuts with castle nuts. for the $20 bucks its easier to just buy the kit than source the nuts lol
-Either Im polishing up my pro armor belly skid or more than likely I found this company called BCC that makes very nice poly skids..I think 3/8" is thick enough but they do have a 1/4" and 1/2" option
-I have had enough of bending the swingarm skid. The best one was PRM and sadly they went outta biz and mine is pretty beat by now. I wish I had someone who could bent up alum and fab up some new ones. So Im going to use a glann one. the design is steel so its very strong and you use a poly or AL sprocket guard. Close possible 2nd idea is the lonestar setup with is similar to PRM but steel
-Poly sprocket guard-really interested in this setup. Ive bent to many skid plates on the rocks in PA
-my pro armor nerfs are toast, only set i like and seem decent are made by xfr..the pro armors were a beast so im hoping these are good. otherwise ill pay a fabricator to fix those pro armors lol
-Send my shocks to hygear suspension to be rebuilt and slightly revalved or sprung. rear is slightly to soft and fronts are too hard all the way on soft.
-powdercoat frame, arms, stem. im thinking of going all black, all dark grey metallic or go black or grey and do the a-arms in honda red. Grey color: Prismatic Powders - KINGSPORT GREY

So anyways thats the plan. Too damn cold here at 9F right now to ride so not like I need to go anywhere. Plus theres always the 400ex to ride.

Im also SUPER tempted to buy white plastics, do the frame red and powdercoat the wheels gold to mimic the old 250r-but by the time I do that..another 1000 bucks of junk that doesnt do anything but look nice. Im going to sand the plastics down and heat them up with a torch-it works very well to restore them.
 
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What do you think caused the piston to valve issue with your Athena 490 kit? My Athena 490 13.5:1 CP kit should be in soon and I’m thinking about doing a manual cam tensioner to help avoid the valves hitting the piston, I know there are other factors that contribute to that but I know that’s one good way towards preventing it.
 

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Truck Yea
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5,790 Posts
Discussion Starter · #3 ·
I and my engine builder believe the stock tensioner failed. Build was brand new build with less than 10 hours on it. There is no other real explanation we can figure out besides it jumping time. I have had them fail randomly before too. Once on a trip to glamis (we truck the stuff out there), while warming it up to load it it began to make noise from the valve train. Its a non refundable thing, so I put it on a truck and bought a tensioner with me for later. Slapped it on and done.

Went to glamis last year, it blew up 10 mins into riding it. BUT there is a chance of mitigating circumstances, 3 months prior a dirt bag stole my quad and we believed the head gasket had failed (dont use the pos paper athena gaskets buy cometic) and the thief beat on it. Either way it failed due to a valvetrain issue

I went with a more mild build to hopefully
1. get more time out of the engine before rebuild, its no fun tearing it down basically every 3 months
2. less chance of failure.
3. manual chain tensioner..so the spring loaded stock one cannot fail if you dont have one lol.

keep in mind a 490 is a 100mm piston, (that is alot more weight even with a better piston) slapping around in there. After a long discussion with the guy who actually does all of my porting, and builds drag bikes he figures the parts wear faster and easier. We had planned on rebuild with piston drop every 25-35/hr depending on wear, crank every 50/hr and cylinder too depending on wear. I did a 470 kit which is only 98mm but I should get more longevity out of it, we figure 50-75/hr before piston drop. I had well over 125 hours before the crank just randomly let go on the stock setup with just a piston drop maybe at 50/hr. Who knows how many hours it had since I bought it used, it was clean but ya never know.
 

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Truck Yea
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5,790 Posts
Discussion Starter · #8 ·
uh, could ya please delete your posts and put them in your own build thread?
 
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