Replacement Engine Flywheel mismatch questions

fergy59

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Howdy folks,
I have a Dixon with a locked B&S 28Q777 that I'm replacing with the recommended B&S 33R877-0003, with instructions to reuse the flywheel and alternator from the old engine. The Dixon was given to me by good friends, elderly lady who's husband had drained the oil for an oil change and forgot to add new oil, so it locked up tight next time she tried to mow with it.

The old engine has a 16 amp alternator and the new only a 9 amp. Thus the reuse of the old parts on the new engine. So, I've swapped the alternator and voltage regulator and was putting the old flywheel on when the thought occurred to me to lay both flywheels side by side and compare them. I immediately noticed that the outside magnet that sits on the rim of the flywheel to fire the magneto coil is in a different orientation compared to the flywheel sheer key slot. I mean it is way off, maybe a third to half way around the flywheel compared to the old one. I verified that I'm not insane and laid a screwdriver against it to make sure I was looking at the magnets on each of them and the screwdriver snapped up against it like it should on both.

It seems to me that if I install the old flywheel on the new engine the spark timing would be way off, right?

So, I flip both flywheels over and inspect the alternator magnets and they seem to be identical in size, and in researching this last night I read on the B&S Alternator replacement guide "The 9 and 16 amp regulated systems use flywheels with the large alternator magnets." The old engine is 16 A and new engine is 9 A.

It would seem to me that I could use the 16 amp alternator from the old engine and the new flywheel in combination since the alternator magnets are the same size and the engine timing would then be correct, right? (I didn't want to install the old flywheel just to see if it worked because I believe having the timing that far off could potentially cause damage??) Have any of you experienced something similar?

I've asked this question on the B&S support Q&A as well as sent the support techs a message asking the same question. Just thought I'd try here and see if anyone has experience with this.

Thanks in advance!
fergy
 

ILENGINE

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How about supplying the type numbers after the model number on the old engine so we can pull the diagrams up ourselves.
 

NorthBama

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The difference would be in the alternator wire winding, if the magnets are the same. I have changed to the yellow connector with matching voltage regulator
 

fergy59

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Thanks for the quick responses. the type number is 0678.
 

Tinkerer200

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NO, you can not use that 33 series flywheel on the 28 series engine which is why the key/magnet spacing are intellectually different. You can use the original 9 amp charging system of your 28 series OR you can use the stator and regulator from the 33 series engine with your 28 flywheel and, depending on the inside magnet size of the 28 series flywheel, get either 16 amp or 9 amp. Nine amp will run your electric PTO, charge battery, etc.

Walt Conner

Well I tried to delete this post but couldn't. I reversed the engine designations but the same applies just switch my engine designation.
 

ILENGINE

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From the briggs dealer website is shows the recommended engine is a 31L777-0136 pr 31S977-0006 which doesn't mention replacing the flywheel or stator. the 33R877-0003 is a different crankshaft and flywheel, so the key orientation could be different. Unless you have a very heavy electrical load you should be able to use the 9 amp system that came with the new engine and be fine. The 16 Amp system and regulator is possible but you will need to use the 33 flywheel.
 

fergy59

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That is interesting information that you got off the B&S Dealer website. I did my inquiry with brandnewengines.com and took their recommendation on the engine I bought. I should have joined here first! Thankfully it looks like I can make it work though. I've already swapped the alternator and regulator. I will put the new flywheel back on and I should be in pretty good shape.

Thank you all for your quick responses and valuable input. I really appreciate all of you!

One more thing: Does anyone know the flywheel bolt torque specs for the 33R877-0003?

Thanks,
fergy
 

ILENGINE

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110 lb/ft is the flywheel torque spec
 

Tinkerer200

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By the way, what Dixon do you have? I have some new and used Dixon parts left if you are in need of something.

Walt Conner
wconner5 at frontier dot com
 
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