Bushmechanic Mongrel 628 Trailbike

bits of this build don't really fit anywhere so ill put them here

I'm building a 628 from bits i have laying around, only stuff i really had to buy were cases head crank/piston.

bushmechanic said:

Scored a smoking hot deal on Ebay, absolute best ever internet buying experience, no BS listing good price 4 days to get here from the states beautifully cleaned parts in top condition you could eat off these! and very well wrapped too. never seen anything like it before 8O 8O

lineaweaver big valve racing head

mint 01 650 cases... they are in better condition than my 08 cases

:

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Big thanks to Mopwer for a smoking deal on these parts.. best ever internet shopping deal.

I think I started on the crank first

http://husaberg.org/mechanical/17329-balancing-80mm-650-crank.html

bushmechanic said:

cut off the counterbalancer drive gear and champhered a lead in for the oilseal

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steel sleeves in the cases to house 22206 spherical roller mains

http://husaberg.org/mechanical/17170-definative-main-bearing-thread-8.html

bushmechanic said:

drive side

drilling oil pressure gallery to the drive main

the old cases don't have the drip feed to the RHS main so I drilled one, will make a dam to catch more oil

decide to install a second piston

sleeves

RHS main bore with sleeve

LHS main with 1mm diam jet

3.5 thou interference fit between the cases and the sleeves

need to go back in the mill and be final sized to a 2 thou interference fit with the bearings.

also re machining the oil pump cavity to take the 15mm wide ktm atv rotor

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Valve Spring upgrade

milled out clearance for the KTM Dual valve springs, can also see the small pocket i put in to take the pivot for the newer cam chain tensioner



checking seated force in the CNC mill



checking for maximum travel from installed height to coil bind



measured 13.5mm

Rocker arm damage from failed Cam follower

intake cam lobe had failed in this engine, intake cam follower bearing was stuffed

the rollers gouged out the rocker arm sides



resurfacing

http://husaberg.org/mechanical/1085-crankcase-venting-101-a-9.html#post150131

bushmechanic said:

second reed valve 02 650

free HP no blowby and still allows oil mist lube where it is needed

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finally found some old parts that even I think need a clean

that took a while and its still not finished





now i know why "real" mechanics are so grumpy... spend all day making things look good on the outside to convey the impression of competent work inside LOL

crank endfloat

Thanks Goose, there are heaps of way more talented people out there, im just a dirty ol engineer

made a spacer and set the end float at 0.1mm for the 22206 spherical rollers



gearbox stuff.

http://husaberg.org/mechanical/17999-bulletproof-gearbox-upgrades.html

my engine and Tyre choice have a habit of destroying rear hubs, rear spokes and ripping the gearbox in half. (105mm bore and bolted paddles)

Ive had 6 gearbox failures In Total, about half of those with the 100mm bore and knobbies but none in the last 150 hrs with a bolted paddle, 75rwhp and a few tricks.

first time it broke was at 160hrs as built from the factory, i screwed up and landed a big bastard flat jump with a bit too much throttle on then on landing the G force on the lever shifted into 3rd .. bang. this happened a second time after a tiny stick flicked up off the front wheel and hit the shift lever

so I looked into the shift star and detent arm. ours is different to almost every other bike. the spring is softer and the shift star is very pointy without the traditional double curve.

that will make more sense when I add more pics tomorrow

tapped a 5mm thread into this hole for a 5mm CSK bolt and used a 2010 KTM 450SX detent arm spring. approx doubles the force on the arm



reprofiling the shift star more in line with other bikes



more pics to come plus circlip upgrades and hardness testing/retempering of the 3rd and 4th sliders

this shows the basic difference, other bikes have a double profile on the star





when you shift gears your input does not actually slide the gears into place, what you do is put the detent arm over the top of one of the points.

the actual shift is done by the detent arm spring so when you have a double profile it can wait for the "right" moment to slide

the berg star just slams it straight in... it is faster.

another issue is the circlips being too pissweak

these are the 08 clips from my bike after the first failure.



the 08 clips are much tougher than the pre 08 clips

tip from KTM talk via craigy was both are crap compared to the kawasaki clips (92033172)



there is an opportunity to use one of these locking stop discs I made on the output shaft, can only install one of them.

I still have one left from back in 2008 to go in my 628







so with the shift star and detent arm fixed (in 2008-9) there were no more failures from the bike shifting itself into gear at the wrong time and the upgraded clips have not been a problem.

but about this time I put the 105mm piston in and started running bolted paddle tyres.





now the gears would just rip in half under load, I sent one box away to be shot peened crack tested hardness tested and cryogenically treated. seemed good but the hard facing flaked off 5th .. it was an old gear, maybe was due to go anyway.

the last mod was just take a standard box (no cryo) and re-temper one of the gears (4th slider) in an oven for 1 hr at 250 deg C

with all those mods Ive had a good run of 150 hrs with the big engine and the paddle tyre although i mostly run in 5th gear

I picked out a set of gears today for the 628 build http://husaberg.org/mechanical/17998-bushmechanic-mongrel-628-trailbike-2.html#post150233

and re tempered some of them in the same way, will be changing gears more often so did 3rd and 4th sliders and the gears that engage into their teeth , 5th and 6th.

they tested 63-65 HRC before and 58 HRC after. polished one side before they went in .. the flash is deceiving, the color we are chasing is dark purple.






oil pump mods http://husaberg.org/mechanical/17851-oil-pump-upgrade-15mm-wide-2.html#post150251









testing the cracking pressure of the valve



put the oil pump cover on and used compressed air

OEM was 13-15 psi, i have it set at 35 psi, a bit over 3 lbs force from the spring is about right

Pro X piston

got my pro-x piston from jawzys ebay shop .. good service

it weighs about the same as the elko but is 0.1mm taller .. bonus





pin is heavier than they speced

Trick Titanium wrist pin

I had trick titanium make me this Titanium pin in 2009

decided I didn't want to use it with the 105mm piston

it is very very well made .. T17 with DLC and c33 hardened end caps, should have the same fatigue life as a steel pin if subjected to the same deflection

since its not as stiff its about 1/2 the life expectancy of a steel pin .. 1/2 of forever sounds OK

due to the greater deflection it needs a larger clearance in the little end of the rod and inside the piston.





weight is 40 gm.. apparently the wossner pin is only 60 gm which (if true) makes the Ti pin a bit overpriced. mine was about $100 but i think they want 200 now.

tourist said:

Keep 'em coming!!

Looking forward to seeing what you're doing about the suspension especially.

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actually im not looking forward to that bit much .. the WP shock is off a 2002 model .. I have an elka quad shock that will probably be more fun to make work.

finding true TDC



made a tiny TDC locating screw setup to speed up assembly ,