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    Re: Rockhound IV ~ Z-434-powered woods buggy
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    Finally opened up the engine. Been a little worried about how it's been holding up with having lost the coolant twice now. No sign of any metal in oil, including the oil tank, oil filter and in the bottom of the clutch side. Oil itself is pretty grey looking, even though it was fresh, i was pretty hard on the clutch this time around.

    Timing chain adjustment was on the last couple notches, chain was on the noisy side, so that's getting replaced and the automatic tensioner will be modded to a manual deal.

    Good news is that it has a set of Hot Cams brand cams in it, older style Stage 1 designed to give a 3-5 tq/hp boost from 4k-up rpm. Between the Athena BBK, cams, exhaust system and oil tank, the aftermarket parts alone tally around $1,200 plus, not a bad score for a $900 full quad! Also sold a couple leftover parts already!

    Probably going to pull the head when the chain arrives to make sure it has adequate valve springs and hopefully upgraded valves as well. i've already revved this thing over 11,000 rpm (or so the Trailtech says) a few times without scattering it, so i'm pretty sure those bases have been covered.

    New, better bearings with additional dirt shields and cassettes instead of stamped steel flangettes on their way from reiken racing ... no more pressure washing in that area ....
    Last edited by Xbird; 08-04-2015 at 06:39 PM.
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    Re: Rockhound IV ~ Z-434-powered woods buggy
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    How do your cylinder walls look? Did you do a compression/leakdown test prior to opening it up? Being you know it's bored out, and we have kind of similar engines I was curious what psi you got. I can't find any real psi specs for my Polaris 500, but in forums, it looks like 100-125# is common. I get 165# in just 2 strokes! The kid I bought it from was no motorhead, but he said when he bought it slightly used he was told it was bored to 525cc. That may give me a clue if yours was around there.
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    Re: Rockhound IV ~ Z-434-powered woods buggy
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    Mine's actually a bolt on athena 434 bbk jug and low compression (dished) coated forged piston. nikasil coated bore looks good, no scratches and piston feels good in the bore. about a $500-600 kit.

    Turns out the chain was only slightly worn, the front guide the tensioner presses against had a big divot in it. Apparently there's an issue with these engines where the front side of the chain slacks up on fast decel from WOT, the spring loaded automatic tensioner ratchets in more clicks and ends up with way too much pressure on the guide. Pretty soon, the tensioner is all in, and the chain either stretches or the guide deforms and you end up with a loose, noisy chain.

    With a bit of mod work it's easy to convert the auto tensioner to a manual, that's on the to do list today. And yes, the garage is about 20-degrees hotter on the slab than it is outside today ...

    I also discovered that the CDI is an aftermarket piece, unknown variety, but it does NOT have the stock 9100-ish rev limit. The valves and springs appear stock, and the top of the piston has a nice gouge as does the head where something went through it with the PO. Thankfully, the damage isn't anywhere critical and i smooth the gouged down on the piston to eliminate a potential hot spot. This thing may have lunched a valve at some point. Right now after checking and shimming the valves, i'm inclined to think they're stock and i have to be really careful with it since i've already run it past 11,000 rpm and the stockers are NOT designed for that!

    T-stat was blown out, that was probably my doing with coolant loss. I just chopped and welded a 27mm wrench, finished torquing the lock nut on the stator side and am buttoning up the top end.

    All my jackshaft parts are in, I may have this running again this weekend. If it survives the 7-miler without scattering, i'll do valves and springs over the winter.
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    Re: Rockhound IV ~ Z-434-powered woods buggy
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    LOL, 2,000 rpm over rev with stock springs that's pushing it for sure. My brother has a piston from his old Honda 550/4 with the valve welded right into it. Try not to do that.
    Yea it's hot as a beatch out there again. I just can't take it like I used too. If I have a shop at my house in Thailand, it will, for sure have A/C...and Dancers
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    Re: Rockhound IV ~ Z-434-powered woods buggy
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    AH HA, so that's what those big lumps on your tie rods are. I love that idea. Ads a nice "give" point rather than a bend point. Did you make your own using springs or buy them?
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    Re: Rockhound IV ~ Z-434-powered woods buggy
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    I made them from fox/polaris 600 indy style sled shocks--the pretty white with pink springs ones. .... they use the shock shaft with the piston on the end with a series of rubber bump stops stacked on either side of the piston. there's about 1/4" of "goosh" when hard cornering, not enough to screw up your direction of travel. in a hard hit i set them up to have about an inch of give in either direction.

    I started with ball joints, snapped a few then went to heims, but kept bending my steering arms. made aluminum through bolts for the heims, but they sheared a little too easily. I did 2 in a 5 lap race and the last one was pretty toasted by the end, for racing, it took too much time to swap them. (5 minutes). No more goofy steering issues since i made these and i have slammed a lot of rocks, stumps and trees. You should be able to find a thread titled "damper rodz" in the suspension section that shows how i made them.
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    Re: Rockhound IV ~ Z-434-powered woods buggy
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    starter relay says .... "click click"
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    Re: Rockhound IV ~ Z-434-powered woods buggy
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    After spending 56 on a starter and 50 to overnight it, now goes vroom vroom! Thankfully I sold the LTZ's swingarm yesterday to offset the cost and cover the race entry and fuel, otherwise the other half would be twice as pissed as she was last night when I fired it up to tune it at 11pmb .

    Guess it's all for the better, if it had started with the old starter, with my luck it likely would have failed on the starting line.

    Main issue now is what i swear is a rod knock. Did the valves and top end, it isn't that, piston slap or the timing chain or an exhaust leak. Going to cross my fingers for one race!
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    Re: Rockhound IV ~ Z-434-powered woods buggy
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    Wishing you good luck Jim! Are these engines hard to come by?
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    Re: Rockhound IV ~ Z-434-powered woods buggy
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    Thanks, i need some this season.
    Not so much as the $s to get them .... Just gave it its first test thrash. Didn't clean the carb, giving me some hard starting fits, seems like the pilot circuit might need cleaned again. Carb has sat since july. for as loud as this thing is, and the way it rips, i'm half wondering if doesn't have a stroker kit to boot. wish i would've measured the piston travel while the head was off. was also fun to hear the shift link rod rattle on the chain after popping off the shift arm, ... someone forgot the clip. At least i'll have one more afternoon to tweak on it. Did quite a bit of work on it, i'll have to take some pics.
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