Bolens Diablo Rouge and Hus Ski Discussion Forums

Finally got the time to pull the engine last weekend and none to soon. I knew I had crank problems, but there was more to it than I thought . I put this engine together 8 years ago and it's run hard. At the time it was all I could find. There was play between the case and the outer bearing race magneto side. A good crank from another engine was scored where the seal rides (clutch side) , when I pulled the crank bearing. I made repairs as well as possible and it held up well. I suspected crank seal problems last winter and here we are. I found the play was back magneto side, the crank bearing had spun on crank clutch side and the piston and cylinder were none to healthy. Ouch! I think leaking crank seals ( because of the play) caused the piston damage, but I'll be upping the oil mixture a little just in case. I had an engine rebuild in the plans , but for this winter I have what looks like a good used engine to drop in . Just in case though , keep your tow rope handy Barrie. Did I mention the cracked front motor mount? Check out the pictures. See you fellows next month. I hear Randy is bringing friends. Roy.

Here are pictures of the piston and cylinder. Exhaust side. Too lean or not enough oil or both ?

I too have seen a few bearings loose in the bore. Only a few where I actually had to replace the casing. Loctite makes a bearing retaining liquid made for taking up clearance in a bearing bore and that is usually enough to make the bearing tight again. Regarding the worn seal area on the crank, an SKF Speedi Sleeve takes care of that problem for good.

So to the question of too lean, not enough oil or both. Hmmm. This I will say. Every motor that comes through the Diablo shop gets the crankcase pressure tested.

Remember early on when this forum was new, we spent a lot of time talking about carburation, timing, spark and fuel mixtures. Why a motor runs good cold but not hot. Why a motor runs good hot but not cold. Motors where it never seems like you can find the sweet spot with the jets and so on. After a lot of trial and error, my opinion is much of those symptoms were a result of leaking seals, gaskets or something more severe like a casing leak or crack or bad cylinder head. Since I've been pressure testing the crankcase, I've found all kinds of leaks I would have never thought were there. And after I get the motor sealed up and it is leak free, it almost always starts up and runs pretty darn good with the factory settings of the carb jets.

To pressure test a crankcase, I put port blank covers over the intake and exhaust. Make sure the surfaces are clean and you are using new gaskets. Have the plug installed and tight. Pump about 5 psi of air into the pulse port and if it holds without bleeding down, your golden. If it leaks down, get out the soap solution and find the leak.

Good advice Bruce. Perhaps I can salvage that crank and case. I have some of that Loctite in the garage from a previous repair. My covers are on the used engine to check for leaks next and then back together. Roy.

Leak check was good. Test run on the front lawn was good. Now all we need is snow.

The forum was a great help when I was working on this engine. I changed the clutch side crank seal first and installed it the same direction as it came out, not remembering the thread on this topic.
All the original 54R Diablo engines seem to have had these seals installed backwards from the factory. The manual says spring side in for both seals and is correct.
Info on setting the points and timing was also a refresher that I needed. See you in Finch. Pray for snow. Roy.

Hi Roy, Bruce, et al

I finally had a chance to spend some time on gogodiablo and saw your post.

I agree with Bruce: I would consider it a leakage issue, not oil.
Everything that I have seen and done over the last few years, particularly with vintage bikes, leads me to believe that if you run good quality oil, particularly synthetic, the ratio is not critical (I know, on some forums, the discussion of what oil, and what ratio can rage on for months). In other words, if there is some oil at all, under normal running conditions (ie: not flat out for long period) you will not get the scuffing that you show in the photos. At a cross-country race in Mass. a few years back I forgot to fuel up at lunch. Ran into a guy on the trail with generator (straight) gas. I topped up from him with no issue. I have also heard stories of guys who put in straight gas at a gas stop (enduro). It was only when they got out onto a road section that the engine seized.

BTW the original synthetics were developed by the Germans in WWII. The purpose was two-fold: alternative to petroleum (shortage), and for their air-cooled aircraft: they wanted something where if you were shot up and the oil was all gone, they could still limp the plane back to France, with no oil pressure. After the war, synthetic technology was further developed in Sweden, where Saab and others were producing 2-stroke automobiles. A lot of the good stuff, including I think some made for Stihl, are designed to be run at 100:1!

re: crank bearings. I am currently rebuilding an Elan engine. The PTO side bearing was loose in the case. Back in the day, the factory fix was a "polymide plasic insert" for the later models. I did locate the plastic insert at Winners Circle in Toronto. Sent it all to CVTech for machining. They did not use the insert, but rather machined the case and used a slightly oversized roller bearing (as opposed to the ball). I am currently in the process of re-assembling this engine.
I would suggest you consider this for your motor as a long term solution that would be better than stock, in my opinion.

Mike