DV20 flywheel

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neil_s

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Evening all ........

I need to get the flywheel off my Bukh DV20 - any tips, please?

I have a problem with difficult starting. I resorted to a can of easy-start this year, and also had a good crop of cream gunge in the rocker box. Low compression, due to leaking piston rings is the problem. I am hoping that I can get the pistons out without shifting the engine off its bearers. I have already got the cylinder head and sump off, but a bit more room is needed to get at the big ends.

Cheers! Neil
 
The six unbraco flywheel bolts are torqued on to 60 ft.lbf and are also sealed with loctite. You will need a proper tight fitting hex socket and as long a handle as you can manage to loosen them. Not difficult with the right tool. When replacing the flywheel it is imperative that you seal each bolt with loctite and use a properly adjusted torque wrench to tighten them back to 60ft.lbf, as the consequences of a flywheel coming adrift at speed are not to be considered. Incidentally cream gunge in your rocker box means you have water in the engine. Most likely the water pump seals are gone, with very often the pump drive shaft bearings also gone. The water would certainly make your engine hard to start. You need to sort out the water problem, and then flush your engine out at least twice - use a 50/50 oil and diesel mix and run for about ten minutes. Change the oil filter each time, and finally fill with fresh oil. Best of luck
 
Bukh recommend changing the unbraco bolts although I have reused the old ones a few times. Another tip is to run a tap into the bolt holes in the end of the crank to clean them and give them a good wash out with acetone or thinners to make sure they are really clean. Likewise clean the bolts themselves before refitting if using the old ones.

Tom
 
The flywheel did come off mine - the unbraco bolts do break! Our local engineer also recounts one coming off at near full throttle - and going straight through the workshop brick wall, so getting the bolts set up is essential. As ladyB points out, a good quality tight fitting allen key is needed for both removal and replacement because of the torque needed.

Removal once the bolts are slackened is usually simple enough unless there is much corrosion - the wheel seats over the end of the crank, and should come off reasonably simply.

Don't go hitting it directly with a hammer either to loosen it, or to reseat it, as the casting can and will break. If it will not come off, and you have to be violent, protect it with a piece of wood, and hit the wood, not the casting.

Getting it back into position can usually be done by drawing it in with the bolts; once it has seated, slacken each bolt off again before torquing it up to the correct setting. I dont think the Bukh book specifies this, but I tightened them in opposite pairs to reduce possible strain and stress on the bolts and the casting while setting up, and to ensure the boss pulled down evenly over the crankshaft.

The book does specify replacing the bolts each time, but our local Bukh man said he had never been asked for them. Perhaps thats why mine came off in the first place!
 
Many thanks for the tips, all. I have a long handle for my socket set.

Lady-B - I replaced the water pump seals only a couple of years ago. I think you get cream gunge if the blow past the pistons gets too much for the breather pipe. There is quite a lot of water vapour in the exhaust gasses and it all collects in the rocker box.

Cheers! Neil
 
Sounds like your crankcase breather may be blocked. Oil sludge tends to collect in the valve and block it. Make sure it is clean and operating correctly. This should eliminate the emulsion, unless as suggested your water pump seals have failed or are reversed. Don't assume that replacing them two years ago has fixed the leak - if the shaft was worn the new seals will do nothing.
 
Problem with taking the flywheel off is that the bolts are torqued to 60ft/lb as has been said and you have to hold the wheel against the spanner removing them. It is also a heavy bu**er even when you expect it to be you can still get a bit of a fright.
 
to hold the flywheel still, get a plank underneath and have someone stand on it. The plank can engage the starter teeth to spread the load, no point loading on single tooth etc, no need for tourniquet on belt. Lunge at each bolt to use dynamics to help uncrack them. use half inch drive socket set 8mm hex and big lever. Wiggle the flwheel, tap it with leather hammer. If it wiggles at all persevere and it will come off. If necessary make a thick extractor, one hole in the middle for a big bolt and nut, two holes at least outside to match the oriiginal fixings. the centre bolt bearing on the shaft should drive it out.

otherwise ring BUkh Uk in Poole . They are really helpful.
 
Neil

The only DV I ever played with did not have a big nut!!!! The flywheel was held on to a spigot with several HT allen bolts.

Small tip... DO not damage the spigot area and ensure the CORRECT bolts are used to put the flywheel back in the CORRECT position and cheque you use the correct torque as advised by the engine builders. Tighten up in a similar way to a cylinder head IE opposite bolts taking the torque up gradually as you rotate around the 5/6 bolts.

The reason I was called was that the owner had done work and the flywheel was wobbling....Got him to stop the engine as soon as possible but it was a bit frightening when the flywheel came off at about 1000rpm and fortunately came to a rest between the bearers /forums/images/graemlins/smile.gif
 
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