Stihl BR 400 blower- Update

[trooper1954]

Hi all,
Further to several posts I've made over the years about the above captioned blower, I'm finally now almost at the stage where I'm going to replace the woodruff key myself after lapping as suggested in another response. Problem is I've reached a stage where I cannot get any further....from the photos you will see where I'm at....I'm not really sure how to get to the shaft so's I can replace the broken key.......do I need pullers to remove the flywheel? in the first photo the round thing in the middle seems really on there tight....
Any help would be appreciated....Thanks

 

[PCustoms]

Can you link or combine this with the previous posts about the blower?

 

[trooper1954]

Can you link or combine this with the previous posts about the blower?

Sorry PCustoms.....not that tech savvy....can someone advise please how to link? Thanks

 

[PCustoms]

Sorry PCustoms.....not that tech savvy....can someone advise please how to link? Thanks

Thread 'Stihl BR 400 Blower keeps breaking woodruff key' https://www.garagejournal.com/forum/threads/stihl-br-400-blower-keeps-breaking-woodruff-key.532009/

 

[trooper1954]

Thanks for the link PCustoms

 

[rd65]

Put the nut on loosely, then hit the end of the crankshaft with a hammer. The flywheel should come off.
Nut is to protect crankshaft threads. A brass hammer would be helpful as well.

 

[rd65]

Only info I could find on Stihl site. I was hoping to find a technical bulletin for this.

 

[PCustoms]

@trooper1954 are you trying to take off the flywheel in your first photo or the blower in your 3rd?

 

[ericm]

Stihl writes very good service manuals. You need one.

99% sure you will need a puller for the flywheel and likely for the blower wheel too. I'm not sure how hitting the crank will remove the flywheel. It also seems like that could damage the crank bearings.

 

[rd65]

Stihl writes very good service manuals. You need one.

99% sure you will need a puller for the flywheel and likely for the blower wheel too. I'm not sure how hitting the crank will remove the flywheel. It also seems like that could damage the crank bearings.

I will look at the one I have apart at work, it is a BR320 but shares the same flywheel. Most Stihl small engines do not use a puller. This pic is not for a BR but for FS trimmer. The puller shown is just an extension that threads onto the end of crankshaft. The shock is what loosens the flywheel from the crankshaft. Stihl site does not have the service manual linked to parts screens, unit is too old. Like I said above, I have one of these units apart and will give it a look tomorrow. Flywheel part number is 4203 400 1200 for a BR400-Z.

 

[trooper1954]

Thanks to everyone for the help and advice......I ended up buying a harmonic balancing puller and will be removing the flywheel later today. PCustoms.....the flywheel in the first picture.
I just need to lap the shaft and inside of the flywheel and then replace the woodruff key which I have.
I will then use a torque wrench to tighten the nut.....something I haven't done in the past. maybe that's the problem, if the nut is only tightened by hand but not with a torque wrench, the flywheel maybe a little loose and so the key is taking too much torque and breaking. I'm going to torque to 17.5ftlbs....I think I've seen that this is the correct torque setting for this.
Thanks again

 

[ericm]

The key is just there to locate the flywheel. The taper is what's supposed to keep it in place.

 

[trooper1954]

So I've removed the flywheel and discovered as expected metal shaving debris inside the housing...(see photos)
I assume this gunk needs to be cleaned off the inside of the flywheel before I start lapping? Also, the broken key does not want to come out....I tried a really strong magnet but no luck....any suggestions??
Thanks

 

[rd65]

small screwdriver or punch and a small hammer

 

[theoldwizard1]

Put the nut on loosely, then hit the end of the crankshaft with a hammer. The flywheel should come off.
Nut is to protect crankshaft threads. A brass hammer would be helpful as well.

The nut should be screwed on just until the top of the nut is level with the top of the cranks shaft.

On good smack with a hammer should loosen that flywheel.

 

[hans109h]

Stihl writes very good service manuals. You need one.

99% sure you will need a puller for the flywheel and likely for the blower wheel too. I'm not sure how hitting the crank will remove the flywheel. It also seems like that could damage the crank bearings.

Every action has an equal and opposite reaction. The fact that the taper holds the flywheel by friction works against itself when the force of a blow to the nut has to go somewhere. The force isn't enough to push the flywheel "further down", so it results in the friction being released and the force sends the flywheel the opposite direction. It's similar to removing seized rotors when doing brakes. Just smack it with a BFH.

Hans

 

[trooper1954]

I've got the flywheel off, I just need to clean the inside of the flywheel (see photo above)
I'm thinking I'll use emery cloth as I've tried with wd40 and brake cleaner and it's not moving it.....any other suggestions?
Thanks

 

[PCustoms]

I've got the flywheel off, I just need to clean the inside of the flywheel (see photo above)
I'm thinking I'll use emery cloth as I've tried with wd40 and brake cleaner and it's not moving it.....any other suggestions?
Thanks

Why do you need to clean it?

The taper is all that matters I think....

 

[trooper1954]

Thanks PCustoms....I was kinda thinking that...you are right....taper is the important part.

 

[ericm]

Every action has an equal and opposite reaction. The fact that the taper holds the flywheel by friction works against itself when the force of a blow to the nut has to go somewhere. The force isn't enough to push the flywheel "further down", so it results in the friction being released and the force sends the flywheel the opposite direction. It's similar to removing seized rotors when doing brakes. Just smack it with a BFH.

Yea I understand that. But ball bearings like the ones supporting the crank don't like side forces, so whacking the crank with a hammer makes me nervous.

 

[trooper1954]

Well, the blower is re-assembled, but now I have a further issue. When I pull the starter mechanism while it is not on the machine it works flawlessly....good strong spring. When its tighten on the blower housing and I pull the cord it is very hard to do. With the plug out,I assume I should be able to pull it easily...not the case!
When I tightened the flywheel i did it to 17.5 ft lbs....maybe too tight?? I followed the parts diagram carefully on re-assembly, and cannot think why the pull is so hard...wher can all that compression come from unless its being held mechanically somehow?
Once again , any help appreciated....getting a little fried over this project.

 

[trooper1954]

Just wondering, what would cause the pull start to be so hard? The problem I have is that while fairly hard might be normal, I don't want to pull excessively as I'm sure that will break the key again.

 

[PCustoms]

Just wondering, what would cause the pull start to be so hard? The problem I have is that while fairly hard might be normal, I don't want to pull excessively as I'm sure that will break the key again.

Is the starter bound up, or is the engine?

 

[trooper1954]

Starter works fine when not installed.....soon as I attach it to the flywheel pulls out but wont return.....so I suspect the engine??

 

[rd65]

Does the flywheel turn? Since you lapped the flywheel/ crank did the ignition coil to flywheel gap become too small. I use a business card for gap.

 

[PCustoms]

Starter works fine when not installed.....soon as I attach it to the flywheel pulls out but wont return.....so I suspect the engine??

I'm assuming as it pulls out the engine is turning over?

If so you've got something wrong in the recoil starter

 

[trooper1954]

Yes....when loosely put on it turns the engine over, but when firmly attached it binds and the pull rope does not go back into the housing??
I'll make a very short video.

 

[PCustoms]

Yes....when loosely put on it turns the engine over, but when firmly attached it binds and the pull rope does not go back into the housing??
I'll make a very short video.

Take your recoil off and give it a look over.

Thankfully your problem appears to be there, and not a seized engine

 

[trooper1954]

So here's what's happening... works when off the blower.....on the blower but very loosely, and when tightened with cover installed hardly moves at all and does not rewind.

 

[trooper1954]

So I have found a fix for my problem....in order to get the starter mechanism to work I've added three small washers as spacers on the recoil housing screws.
Once I'd done that I put in fresh gas, new spark plug and fired up. The blower started, but immediately revved right up to high RPM ....stayed there for awhile then revs reduced and blower stopped.
This blower has sat for at least two years, so I'm wondering if carb/fuel lines need replacing??
Also, question I have is it seems the woodruff key is holding.....would I be able to start the blower if it was broken??
Thanks

 

[thammel]

If the machine sat for 2 years, I'd say the carb definitely needs cleaning, rebuilding or replacing. I suggest using ethanol free gas and adding stabil to it.

 

[trooper1954]

Thanks Thammel....always use 94 oct here in Canada and for all 2 strokes I use a product called OPTI-2 as an additive....this machine was drained completely when I put it on the shelf so it will be interesting to see what sort of shape its in when I take the carb apart.

 

[rd65]

Does the carb have 2 fuel screws or 1 air screw? Fuel screw carbs are the better ones. Carb should clean up fine. Maybe a kit with the diaphragms and needle. Most homeowner blowers don't get a ton of time on them, so they last forever. We've got 2 BR320s at work that are used for check tools. The City bought them new and they still run fine.

 

[trooper1954]

rd65....fortunately it's the one with 2 screws H and L and an idle screw...would you know if I would be able to start the blower if the key was broken again? And if the key is broken would that give me the high rpm and then dying as a symptom?
Thanks.

 

[rd65]

A broken key will change your ignition timing. The high rev I would blame more on running lean or an air leak. I would start with the carb. Did unit still turn over after stopping? It didn't seize? When you have the carb off you should be able to see the piston skirt. You will get a better view by pulling the muffler.

 

[trooper1954]

rd65, yes....after running at max for 10 secs it died, but would still turn over after...it did not seize. Piston looks good through both plug and exhaust port.

 

[trooper1954]

So the good news....blower is running well. New carb. (chinese of course!!)new plug , fuel lines, air filter, fuel filter. But now have another issue...altho the blower is running well, the idle screw on this new cheap carb. does absolutely nothing!! I've set L and H and its running fine, perhaps a wee bit fast at idle, but that screw does squat turning right in and right out. I still have the old carb, and intend to clean it and maybe re-install if I cant solve this issue.
Thoughts on this.....the never ending story!!!!

 

[thammel]

So the good news....blower is running well. New carb. (chinese of course!!)new plug , fuel lines, air filter, fuel filter. But now have another issue...altho the blower is running well, the idle screw on this new cheap carb. does absolutely nothing!! I've set L and H and its running fine, perhaps a wee bit fast at idle, but that screw does squat turning right in and right out. I still have the old carb, and intend to clean it and maybe re-install if I cant solve this issue.
Thoughts on this.....the never ending story!!!!

LOL, Stihl carbs.....I've bought more of those than I should have. For a Stihl string trimmed and a Stihl chainsaw. I think the answer may be to not buy the cheap Chinese ones. Well, now they may not be so cheap!!!

 

[ericm]

So the good news....blower is running well. New carb. (chinese of course!!)new plug , fuel lines, air filter, fuel filter. But now have another issue...altho the blower is running well, the idle screw on this new cheap carb. does absolutely nothing!! I've set L and H and its running fine, perhaps a wee bit fast at idle, but that screw does squat turning right in and right out. I still have the old carb, and intend to clean it and maybe re-install if I cant solve this issue.
Thoughts on this.....the never ending story!!!!

Sounds like the throttle is being held open a bit so it's not on the stop. You can check visually and see if the arm is hitting the end of the idle speed screw.
Make sure the throttle cable is fully seated in the carb and the inner wire has a bit of slack. Sometimes the chinese carbs are a little different from the OE ones they "replace". I had one that had the L and H screws reversed.

 

[trooper1954]

I looked at the stop and the end of the adjustment screw does make contact with it, but doesn't move at all.
I think its just poor machining, and I'm so I'm going to get a carb kit and and clean and refurb the old one.
Any idea what the H and L settings should be on these carbs.....I have them currently at 1 1/2 turns out from the stop counterclockwise.
The blower doesn't start at the moment despite all the new parts....it ran fine the other day but I messed a little with the settings to try and get that idle sorted and now it wont start.
Thanks.