H70 problem - Snowblower Forum : Snow Blower Forums
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post #1 of 18 Old 12-29-2016, 11:57 AM Thread Starter
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H70 problem

Hello all! First time post for me here, but I'm hoping you can help me out.

I was just given a snapper snowblower model I724. It's in pretty good shape. Was told it had been sitting for many years. After replacing the fuel lines, it started on second pull after priming, but wouldn't run without the choke. Purchased a new carburetor from Ebay and it ran like a top. So now my problem. After our last snowfall it was down to about 5 below zero when I got out in the morning to use my new toy. It started right up, but as I was letting it warm up it seized up. Totally bummed out about that, I went and got my Honda hs-520 to do the job. While it works OK, I really don't like using it.

Anyway, I just got the engine apart today. I found that the crank, rod, piston and cylinder are all in fine shape. The problem was that the camshaft seized up where it passes through the cover. It's a twin shaft with cam mounted pulley. I've tried to force the shaft out of the cover, but it's not moving. Regardless, it looks like I need to get a replacement cover and a new camshaft at the very least. So this leads me to the big questions. Am I going to be OK just replacing the cam? Or should I be looking to replace everything while I'm in there? What would "everything" be? New valves, new piston and rod?

Also, when looking up my engine parts list, the cam is a part number that isn't readily found, on ebay anyway. My engine number is H70-130276N. The cam shows number 33931 on the parts listing. Of course, that's the one cam that I can't find on ebay at all. There are several other cams that show to work on HK70's, but I have no idea if they are all pretty much the same, or if there are small differences making them model specific. I know I'm being cheap, but I like the idea of a $20-$30 dollar ebay cam vs a $100 cam from one of the big parts stores. After adding up the gaskets, cover, cam and anything else I have to get I might be better off with a different blower all together.

Any advice or ideas would be greatly appreciated. By the way, I've really looked into just replacing with a predator, but I'm not sure I want to mess with all the issues that brings up. I may start another thread in the repower forum for that though.

Thanks-
Rod
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post #2 of 18 Old 12-29-2016, 01:11 PM
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Hello and welcome to SBF rack. Was the engine run with low or no oil?

Strange that only the cam seized up. Have you tried soaking the cam and cover in oil or liquid wrench and trying to rotate the cam back and forth? Since the cam is made of steel, chances are the cam will be usable if freed from the aluminum cover and that would be the only part that needs to be replaced along with the necessary oil seals and gaskets. Any aluminum build up on the cam shaft can be removed with muriatic acid and fine emery cloth in a well ventilated area with eye and hand protection.

It would be a good idea to check the valve lash and lap the valves before adjusting the clearance by grinding the valve stems to the correct specs which is .008 to .012 thousandths on each.

http://www.barrettsmallengine.com/ma...headmanual.pdf

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post #3 of 18 Old 12-29-2016, 01:15 PM
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Quote:
Originally Posted by rack View Post



Any advice or ideas would be greatly appreciated. By the way, I've really looked into just replacing with a predator, but I'm not sure I want to mess with all the issues that brings up. I may start another thread in the repower forum for that though.

Thanks-
Rod
I think the predator will be a lot less hassle in the long run, and probably a lot cheaper. Many have done it, and are VERY happy with their decision.

Did you run the engine with low/no oil ?
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post #4 of 18 Old 12-29-2016, 01:18 PM
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Quote:
Originally Posted by RIT333 View Post
I think the predator will be a lot less hassle in the long run, and probably a lot cheaper. Many have done it, and are VERY happy with their decision.

Did you run the engine with low/no oil ?
He'll need the twin shaft motor...Predator only has the one......a good idea otherwise.
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post #5 of 18 Old 12-29-2016, 01:21 PM
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Swapping to a predator is basically out with it being a dual pto setup. Not impossible, but NOT a mid winter project IMO. Best advice I can give is to look for a broken auger snowblower with a dual shaft setup on CL, scavenge the motor. They made them even in 10hp versions so they are still out there. Problem is potentially buying someone's crap and not knowing the true history of maintenance. I've never seen a cam shaft seize at the block. Steel against aluminum friction would usually have the steel win. Normally the power stroke would break something else loose (like the rod). Are you sure a valve isn't stuck/broke that caused the cam to stop? When you took it apart did the lifters fall out, or are they still up in the block. You may have more issues than you think. Pics of the carnage may help some smarter folks advise you in a better way
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post #6 of 18 Old 12-29-2016, 03:02 PM
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I'm pretty sure you can flip the drivetrain so that a single shaft motor spins the drive plate the right direction if you want to try a new single shaft engine.

Doesn't the cover have a brass bushing to support the cam through the cover? I'm kind of surprised that it would seize there.
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post #7 of 18 Old 12-29-2016, 03:29 PM
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I'm betting if you get the cam out of the cover, it could be reused. Find a machine shop and they could bore the hole oversize and press a bronze bushing in there. Probably easier than finding a two hole cover.

X3 was it low on oil?
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post #8 of 18 Old 12-29-2016, 03:42 PM Thread Starter
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Thank you all for the quick responses. First of all, the crank definitely seized up where it passes through the cover. I decided that since the cover was doomed anyway, I would try to get the old cam out. I tried to persuade it out with a brass drift and mallet. That got it out almost halfway, but then the case finally gave out and cracked. No big loss... but I can definitely see where the aluminum build up is on the cam. I will take some pictures, but I don't think I can post them until I meet a minimum post requirement.

I know it wasn't low on oil, but I'll admit that I didn't change the oil before I used it. I have new oil in the garage that I was going to put in... but my grand plan was to use the blower for the day and get it good and warm, then change the oil. obviously not the greatest choice! I figured it would be fine for the day. Last time I make that mistake. For what it's worth, there is a nice slick coating on everything, and even after the failure there are no metal flakes in the oil. My thought is that the oil passage got clogged up in the cover, but since I haven't got the cam out yet, I can't even see it yet to know IF there even is an oil passage in there, I just saw one on the crankshaft hole and assume it will look similar for the camshaft.

Grunt- Thanks for the link. I was planning on lapping and checking the lash on the valves since there's a lot of carbon build up. I'm glad to hear I may be able to clean up the cam I have with muriatic acid. That was going to be my next question. There is no visible wear on the cam lobes, and the cylinder looks brand new. Other than a lot of carbon build up on the piston and intake valve it looks just about perfect. I agree that it's incredibly unusual for this type of failure. I'm a backyard mechanic, but I've never seen this before.

Jtclays- The lifters fall right out, and everything looks great in there. Nice smooth action when I press each lifter up against the springs as well. Valves seem to work great. The cam came out fused with the cover. Even after a somewhat severe beating, the cover won't let go of the cam. Now that the cover is officially garbage, I'm going to trim off the excess cover material so I can get a 3 jaw puller on it and get the cam off and cleaned up. I'm hoping it's going to be fine. I should have probably tried soaking it, but I figured if it's screwed up enough to lock up while it was running at full throttle, that no solvent was going to break it loose.

And on the subject of the predator, the snapper I have has a different style friction wheel drive than the majority of other machines. Instead of the rotating friction disk being mounted on its own plate, that is the rotated into the rubber friction wheel, mine has the rotating disk mounted on the auger shaft with bearings, and the friction wheel itself is moved onto and off the friction disk. Simple in operation, but it's not nearly as easy to get a larger friction disk for mine as it is for the MTD, and other blowers that I've seen on the forums here. In other words, no way to slow it down, or extremely difficult without a lathe or equivalent to play with.

Rack

Last edited by rack; 12-29-2016 at 03:52 PM.
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post #9 of 18 Old 12-29-2016, 03:49 PM Thread Starter
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By the way, before I chose to get medieval with the cover I checked that I could get another one. They are plentiful on ebay, so I chose to go for it.
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post #10 of 18 Old 12-29-2016, 07:26 PM
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Not trying to beat a dead horse, but are you saying the cam shaft seized to the exterior pulley itself?
I just can't see it seizing to the aluminum of the sump cover, but I'm slow so help me.
Did the cam pto drive pulley walk in on the aluminum case? Like you can't remove the cam pto pulley?
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