OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Series 70 crankshaft burred thread

Hi

Any thoughts on crankshaft thread protrusion beyond the bladeholder nut on a V144 with a Mark 3 engine?

Resorted to grinding off the nut due to the crankshaft thread damage protuding below the nut. There wasn�t enough to re-thread but was enough to prevent removing the rusted-on nut using the normal tricks.

The tapered sleeve is 1� x 1-1/4� (25 x 30) and I assume is the standard EN70883B with a non-reinforced bladeholder CA09203B. The crankshaft ends below the bottom level of the bladeholder and therefore the exposed thread receives the brunt on any rough patch rather than the nut, blades or bladeholder.

A Mark Two engine with a different tapered sleeve and bladeholder has no thread protruding. I assume both the Mark Two and Mark 3 have the same crankshaft, thread lenght and taper etc, so it�s just the designed combination of this sleeve, bladeholder, washer and nut that are the cause of the problem.

I imagine just adding a flat washer/s under the recessed nut may effect the Belleville washer and possibly allow the disc to spin. Wonder if some shim brass in the sleeve was worth considering?

Any thoughts on how to protect the thread, other than not to use a �Utility� to mow on rough patches, would be appreciated

thanks

Mark

I usually don't grind off nuts. Instead I split them off using a nut splitter though sometimes I do put channel in the nut so the splitter has better time splitting. Now of course I don't what the clearance issues are either. I have in the past even use a cutting torch to slice them off with damaging the threads but you got to know what you are doing using the torch.

Hi Mark, probably cutting the excess thread off is probably the best idea as long as you remove the nyloc nut first so you don't cook the nyloc up and that you leave about one thread sitting through the nut once you have tightened it home.

I had this problem of damaged threads on a couple of Southern Cross crankshafts. I ended up buying a die the same size and thread type as the shaft. Worked a treat!

Often a cheaper option is to buy a hexagonal 'die nut'. With a button die, you really need the appropriate die holder as well. Essential, if its a 'split' adjustable die.

These die nuts are suitable for restoring damaged threads, though not for cutting new ones.

The crankshaft thread size [both ends] for all Victa full crank engines is 1/2"-16tpi BSF.

For the bottom thread on the PowerTorque engine cranks, it's an M14 ISO metric, but I can't find a reference as to what pitch it is. 1.25 or 1.5mm would be most likely.
M14x1.25 is the same as a 14mm spark plug, BTW.

I had actually removed the nut by grinding down as close as I could to the thread and used a couple of off centre heavy hits on an old chisel to get it loose.

I could then get the nylon and spread the nut enough to get over the "bad" thread. Once off, I had a couple of goes with a triangle file in an attempt to re-groove some of the burred thread, but if I don�t cut it off, will probably need to invest in a re-threading die. Reducing it by about 6mm would line it up with the top of a tightened nut.

I thought this may have been a more �common� issue with the non-gentle use of utility Victa�s in the past, hence the query.

Mark

A number of these nuts I can't remove with my rattle gun, so I either run 4 cuts down each side of the nut keeping away from the thread and then my rattle gun will remove them. My other option is to go to a mates place and borrow his battery one with 1100nm of torque. When we use that one something is always going to give

Hi all,
My cheapie air 1/2" rattle generally removes the centre nut no problem, but not with this full crank that had been semi exposed to the weather for years on end.
I grabbed my emergency electric impact gun that I keep in the boot of my car that runs off the ciggie lighter socket. This one doesn't have the usual series of quick hits per second, instead it operates with a series of heavy bangs once per second. Sounds odd ,but it gradually succeeded in moving the nut after a few seconds of persistence on and off. It was satisfying to see the red oxide dust emanating from the stud with each bang of the gun.

Here I had air flow problems using the low torque impact (250 ft-lb (339 N-M)). It was an air hog meaning it needed more flow then my setup at the time could provide. I actually had air restrictions at the couplers and plugs. What had done without thinking was to installed el-cheapo versions that didn't even match the specs. Even when I brought a 1300 ft-lbs Air Cat impact and it would not even remove my lug nuts from my truck wheels.

I have since resolve the problem by installing hi-flow couplers and plugs and I am still using the same compressor and air lines.

And upgrading was a big plus in more then one way. I just got to be careful removing nuts and nuts as they can go flying rather quickly now if I don't just bump the trigger. Also on some bolts I need to take time for the bolts to cool between impacts so I don't snap them off due to fiction heat.

With muffler that Air Cat installed things in the shop is a lot quieter too. The compressor runs less and I am using 125 ft of 3/8 air line so I can get to most things in my parking lot without using a portable air tank. Mentioning the portable air tank my old el-cheapo impact would drain it quickly so I couldn't even get a job done but the with the new impact I can remove and install a set of three bar blades on the same tank of air. It was the best 200 usd I spent on a tool in the last few years.

So NormK and Mowerfreak you might need to upgrade your impacts and if you are like me might need to save up for it but in my opinion it is well worth the effort as your work will go smoother and quicker.

Just as a follow up on Gadges comment on the pitch on these shafts it is 14 x 1.5

hello, i have a victa 18 special and the crankshaft thread at the top is a bit burred, i know from the manual that i can use a 1/2" bsf die however i am not sure what degree would be correct if this matters. will something like this work?

https://www.ebay.com.au/itm/BSF-Split-Button-Die-sizes-from-3-16-1-all-55deg/401077093226?hash=item5d620ec36a:m:mZsA1jpT0OSI-t09RHiKBwA:rk:2:pf:1&LH_ItemCondition=3

thank you

Hi dmitr, is the nut on or off, how much thread is damaged. Depending on the damage I find it cleans up fairly easily with a 3 corner file, just work your way around it

Hi NormK. the nut is part of the cup. it is off now because when i went to start it it came off. the thread is just damaged a bit at the top. i have tried with a file however it does not work i think i may need to get the die for ebay. will the one at the top work because i am not sure about the degrees if that even matters.

Hi dmtr, if it is just damaged at the top then use a flat file on it and drag the fife upwards, that will help with the bur upwards so the nut can start. If you can't get the nut started the die nut is going to cause you similar problems, you would still have to work the file upwards to get it to bite without it cross threading. Better to get a file you can use often than a die nut you will use once

G'day all,
+1 to Norm on this - I do have 'thread restoring files' on hand here, but a triangular needle file will do the job just fine.

As I've said earlier in this thread, a 'die nut' will work better than a button die here, unless you have the right size die holder for the button die.

Is it just that the top of the thread is burred, from being hit with a hammer?

thank you, I spend some time this afternoon going over the crank shaft with a file. I re tapped the starter cup (witch includes the aluminium nut) by turning it one to another crankshaft secured on a vice using a lot of leverage. This worked for me well. This occurred this morning when I went to start it to test the backfiring. the cup was not on tight by the looks of things and became loose and bored the thread. all good now thank you for you help.