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Allis 620 hydro problems


Josiah deshong

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Josiah deshong

Yeah your right u can see where the fuel pump goes but just no holes but it has an oil filter and it’s on the same side as  cck but whoever had it before had it idiling @ 1800rpm haha but I’ll check those things out it still needs a lot of work done to it , the P.O. had gotten everything close to fitting and I believe gave up I brought it home and rebuilt the carb and it ran and drove after years in the woods I didn’t really notice all the hacking that went on till I tore it apart 

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SimpleOrange
9 hours ago, Josiah deshong said:

Yeah your right u can see where the fuel pump goes but just no holes but it has an oil filter and it’s on the same side as  cck but whoever had it before had it idiling @ 1800rpm haha but I’ll check those things out it still needs a lot of work done to it , the P.O. had gotten everything close to fitting and I believe gave up I brought it home and rebuilt the carb and it ran and drove after years in the woods I didn’t really notice all the hacking that went on till I tore it apart 

Remove half the flyweights the engine has to run twice as fast to modulate the governor, thus we now have 3600 rpm.

Your PO must have done as I did change the crankshaft  for the longer snout, gen sets uses short taper that fit into the armature. Bonus is that they spent it's life tucked inside an RV which when on vacation was plugged into a RV park outlet.

From my observations the Onan cast iron blocks that I have disassembled have all shown very little wear which leaves me to believe the foundry used some chrome in the alloy.

Chevy small blocks that has 0.010 or 0.020 embossed into the rear of the block contained that percentage of Nickel and were sought after by the high performance crowd.

Henry Ford in his Model T used vanadium to lighten and make parts stronger.

The Brits used an alloy called Chromally

 

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Edited by SimpleOrange
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Josiah deshong

Yeah the P.O. uncle told me he had 3 grand in the motor and I thought he was just exaggerating but knowing what I know now he might have. It’s a non smoking great running engine that sat in the woods for a long time so maybe there was truth to it. Thanks for the info. I’m not sure I know what u mean about flyweights but I’ve never had the governor apart yet either but the engine seems to run a lil higher rpm then my 620 cck or maybe it’s the galvanized 90 degree 5 hp Briggs muffler P.O. dished out six inches from the hood on each side 

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SimpleOrange
2 hours ago, Josiah deshong said:

Yeah the P.O. uncle told me he had 3 grand in the motor and I thought he was just exaggerating but knowing what I know now he might have. It’s a non smoking great running engine that sat in the woods for a long time so maybe there was truth to it. Thanks for the info. I’m not sure I know what u mean about flyweights but I’ve never had the governor apart yet either but the engine seems to run a lil higher rpm then my 620 cck or maybe it’s the galvanized 90 degree 5 hp Briggs muffler P.O. dished out six inches from the hood on each side 

The ball bearings inside the cage are flyweights as the engine gains rpm increases or decreases the ball bearings ( flyweights ) interact under the domed cover.

Flyweights is terminology used from the days of steam engines, carried over to modern times.

If all your getting for top rpm is  1800 rpm this tells me the engine was used for generator service and that the governor has ten ball bearings under the cover to change the engine from generator duty and get it to 3600 rpm you have to remove five of the ball bearings under the governor cover.

Below this image external governor that would have been used on either a steam engine or to control the amount of water projected at the face of a Pelton Wheel to maintain generator rpm.

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Small 2 and 4 stroke gasoline  engines may use an air vane governor similar to the one below, these you'll find are tucked away under the air duct cowling.

Older Briggs used a metal vane.

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2 hours ago, Josiah deshong said:

Thanks that’s something I never wood have figured out on my own

Once the timing cover has been removed, now that the timing gears are exposed you can turn the domed governor cover while its still installed. You'll be able to see the ball bearings through one of the open holes on the dome cover

On the 3600 rpm engine there will be a space visible in the bearing cage before the next bearing appears under the covered dome hole. While the 1800 rpm engine has bearings located right next to each other.

If you have to remove some balls and your working with the engine as it would sit in the tractor the camshaft gear will be in a vertical position, be prepared to catch all the bearings once the dome cover has been removed.

To reinstall the governor bearings use a dab of water pump grease to secure each into the cage, that little snap ring is a bit tricky to take off and reinstall.

You'll need a puller to remove the flywheel, after you remove the bolt and washer that secures the flywheel reinsert the bolt so your puller has something to but up against with out damaging the internal threads on the crankshaft.

For those of you that have never used a puller before the tool is a bit deceiving, once the puller is secured you apply some torque to the center bolt then give it one smack with a hammer. If the flywheel does not move repeat the procedure.

Some guys use an impact wrench on the puller to completely remove the flywheel in one shot and this is totally wrong.

puller.png.e2aa408b899e3126ed0ec59379f9feb6.png

Edited by SimpleOrange
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Josiah deshong

I had to wallop my one flywheel several times with pressure from a puller. The P.O. had the flywheel bolt into the crank before the double belt drive pulley am I right that it goes in last after the flywheel and double drive pulley that’s what my manual seems to think but it’s a cck manual

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Josiah deshong

Thanks I thought so but didn’t know if the genset motors were different somehow. This is like having onan technical support on speedial what a lesson I got for ten bucks thanks again

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1 hour ago, Josiah deshong said:

Thanks I thought so but didn’t know if the genset motors were different somehow. This is like having onan technical support on speedial what a lesson I got for ten bucks thanks again

Pay close attention to what Gill writes.  He recently crossed over from another forum & has taken the time to post very detailed posts involving the Powermax tractors & the Onan engines that have never been posted on this site.

Edited by ShaunE
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SimpleOrange

Onan CCK and sister twins use two different length head bolts in each cylinder head, placing a longer bolt where it doesn't belong will bottom out in the engine block.

Improper placed head bolts look and feels proper on the torque wrench, it was not until a day later while re-torquing the head bolts that I had discovered the error. The bottomed out bolts would not budge during the re torque while the other head bolts all turned at least an additional 1/8 turn after the head gasket had relaxed overnight.

 

 

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