I'm assembling a 7900 case and need to know what tool or tools are required. Searched here and on google and wasn't able to find much info. I'm sure there's an assembly tool to pull the cases together.
Dolmar case assembly tool?
- Thread starter ballisticdoughnut
- Start date
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- stihl 034
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redhawk23
ArboristSite Operative
I separated a Dolmar 421 case with a mallet and intend to put it back together with one.
Heat gun or a propane torch plus a brass hammer is all I ever needed. Something to turn the fasteners.
bullittman281
ArboristSite Operative
This is timely.....
I just finished putting a pair of 034/360's back together. The first one came apart and went back together with aftermarket bearings and a big hammer. The plan was to chill the bearings and heat the cases. This only sort of worked and it all got stuck 1/2 way putting the case halves together. Armed with new knowledge I pulled out all the stops on the second "good" one that got all OEM parts. Dry ice is amazing. The local welding supply has both dry ice and liquid nitrogen. The liquid nitrogen is very much overkill. The correct sequence for the Stihl is the fly wheel bearing onto the crank, then the crank/bearing into the flywheel side case half, the PTO bearing into the PTO case half, and then finally pull the crank though the PTO bearing to bring it all together. Stihl uses the oil pump to locate the PTO bearing. This is where disaster stuck on the first saw.
By heating the bearing and chilling the crank w/ dry ice the flywheel bearing will just drop onto the crank. The same for putting it in the case. Heat the case half and chill the crank/bearing and it drops together. Chill the bearing and heat the PTO case half and the PTO bearing will drop in. Hot is only ~200 *F MAX. Be mindful of what locates the depth of the bearing. Stihl uses the oil pump, I'm not sure what Dolmar does. If the case has a step in it or something else... Figure it out and have a plan or things get stuck and the hammer has to come out.
Once the crank is in the flywheel side and the bearing is in the PTO case half the crank is sucked though. There is too much to align to use temperature differential for final assembly. I have a lathe so making pullers is easier. I made a left handed tap for the clutch threads on the crank and threaded a tube to screw onto the crank and pull it through the bearing. With finesse the clutch and a stack of washers could do the same thing. Visit youtube for more ideas. Be sure to push on the inner race when pulling the crank though. The whole goal when assembling the engine is to NOT put axial loads on the bearing's balls. They are not meant for that. And hammers are very hard on bearings. Grease the threads on the crank when pulling it though. They are very fine and you don't want to damage them using them as a puller. They were never designed to do that. Go slow and think it through beforehand and it should go just fine. Dry ice is you best friend. The crank should spin very free if everything is home, square, and centered. Good luck!!!
Bullittman
Edit:
I used supper weather strip adheasive to glue the center gasket to one case half to make assembly easier. On things that don't get a gasket, like Yamaha case halves I use Yamabond. Some other supper silicone stuff would work as well. These are what I have on hand. Also, becarefull of installing the seals. I had to make a seal bullet to put the PTO seal in.
I just finished putting a pair of 034/360's back together. The first one came apart and went back together with aftermarket bearings and a big hammer. The plan was to chill the bearings and heat the cases. This only sort of worked and it all got stuck 1/2 way putting the case halves together. Armed with new knowledge I pulled out all the stops on the second "good" one that got all OEM parts. Dry ice is amazing. The local welding supply has both dry ice and liquid nitrogen. The liquid nitrogen is very much overkill. The correct sequence for the Stihl is the fly wheel bearing onto the crank, then the crank/bearing into the flywheel side case half, the PTO bearing into the PTO case half, and then finally pull the crank though the PTO bearing to bring it all together. Stihl uses the oil pump to locate the PTO bearing. This is where disaster stuck on the first saw.
By heating the bearing and chilling the crank w/ dry ice the flywheel bearing will just drop onto the crank. The same for putting it in the case. Heat the case half and chill the crank/bearing and it drops together. Chill the bearing and heat the PTO case half and the PTO bearing will drop in. Hot is only ~200 *F MAX. Be mindful of what locates the depth of the bearing. Stihl uses the oil pump, I'm not sure what Dolmar does. If the case has a step in it or something else... Figure it out and have a plan or things get stuck and the hammer has to come out.
Once the crank is in the flywheel side and the bearing is in the PTO case half the crank is sucked though. There is too much to align to use temperature differential for final assembly. I have a lathe so making pullers is easier. I made a left handed tap for the clutch threads on the crank and threaded a tube to screw onto the crank and pull it through the bearing. With finesse the clutch and a stack of washers could do the same thing. Visit youtube for more ideas. Be sure to push on the inner race when pulling the crank though. The whole goal when assembling the engine is to NOT put axial loads on the bearing's balls. They are not meant for that. And hammers are very hard on bearings. Grease the threads on the crank when pulling it though. They are very fine and you don't want to damage them using them as a puller. They were never designed to do that. Go slow and think it through beforehand and it should go just fine. Dry ice is you best friend. The crank should spin very free if everything is home, square, and centered. Good luck!!!
Bullittman
Edit:
I used supper weather strip adheasive to glue the center gasket to one case half to make assembly easier. On things that don't get a gasket, like Yamaha case halves I use Yamabond. Some other supper silicone stuff would work as well. These are what I have on hand. Also, becarefull of installing the seals. I had to make a seal bullet to put the PTO seal in.
Was able to assemble the case quite easily by putting the crank in the freezer for about an hour. I then used a heat gun to heat the bearings (already installed in the case halves) to 200F. thing practically fell together. Just needed some gentle persuasion with a plastic mallet to get the case halves past the dowel pins.
bullittman281
ArboristSite Operative
Excellent!!! Sounds easier than the 2 360's I did. Off to the races!!!
Bullittman
Bullittman
Well it’s more like getting ready to go to the races lol. Picked up a 6421 with a smoked piston and cylinder. Turns out it also needed a crank, cases, clutch cover, and a handful of other random bits. Just waiting on some rubber parts and THEN I’ll be off to the races.
