Punsun Kaput!!!

[thundercougarfalconbird]

hi fiddler,the engine parts breakdown shows no thrust washer on the pto end , and i dont remember one in my engine either, i will check my end play, may have room to fit a thrust washer from a kohler gas engine in there

[andrewaust]

Hi Fiddler!


Hope you can sort it all out pal, good to see your getting some help regarding the case donation etc. It's a damn shame when something like that happens. Hopefully you'll work around the problems and end up with a good reliable unit.

I haven't had much feedback on the V-Twin engines, the singles seem like a good unit.


Andrew

[Stuart]

If the engine they got the spare case from is complete you could maybe try getting and swopping the crank/flywheel part. That's gonna be the cause of the vibes right? If it's bad already then the other one maybe better. Couldn't be any worse.
Maybe try and get those parts balanced or checked before re-assembly.
If anyone has a .pdf manual of the Punsen can they send? I need info on this lump.

[Fiddler]

Guys,

Thanks for the input, much appreciated.

Taildraggin,

Thanks for the link for rubber mounts. I had a good trawl around the site. A very handy rescource indeed.
Also thanks for the idea regarding rigid mounting one end and rubber mounting the rest. On the one hand I have concerns about fatique in the rigid mount. On the other hand providing the mount was strong enough, it solves some headaches for me regarding space, sprocket clearance and CVT belt centre distances. Food for thought.

TCF

Thanks for checking the parts list, if there is any chance at all that the cam drive sprocket can pick up on the case, then serious consideration needs to be given to preventing it.

Stuart,

Im trying to negotiate getting the whole short motor from the supplier. He seems very keen to do right by me as a customer but obviously he cant just give me the lot for free. Im sure we'll sort something amicably.

At the moment though Im a bit ambivalent about the unit. On the one hand as the engine is stripped, now is the time to replace bearings, balance the flywheel,pistons, crank etc. Then redesign and remake the mounts. Then possible see if I can find a higher quality fuel pump that isnt prone to dumping fuel in the sump. Then fabricate brackets to prevent fractures of the fuel lines.
I could do all this and invest a tidy sum of my own time and money and then have the crank let go within a 1000 miles. I'd feel a proper fool then.
Maybe its time to do just a basic rebuild and sell the motor cheap as a geny unit to part fund another motor. If Im remaking the engine mounts anyway, now would be the time.
With regards to cranks letting go. I had a crank fail on a 6 pot Gardenor once whilst Tug driving on the River Severn, these things are massive and strong so I know that sometimes these things happen, so I dont want to get over paranoid. Its just that my gut feeling is that this crank design is right on the limit of what it can handle. It copes fine with its intended purpose but just isnt strong enough for our needs.
Only serious miles and further feedback is going to answer this conclusively. Anyone want a cheap Punsun for Research and Development purposes?

[thundercougarfalconbird]

fiddler, i checked my engine for endplay, it seems it has none, i will have to pull the sump cover and check clearences, but from what i understand of that engine design with a ball bearing on the mag side with press fit on the bearing to crank and pressed into the case there is no visable endplay.
is it possible with the cvt system when its shifting it creates massive thrust loads shifting the crank in and out of the ball bearing and slamming it into the pto thrust surface? i do know snowmobiles use a driven pulley that can "float" or slide back and forth on the jackshaft to compensate for shifting and belt flex, they also run alot of massive ball bearings to support the huge demands from the cvt. just some thoughts to ponder

[BoxerOtto]

hi fiddler, boxer otto here, on a slightly different note, before the engine had issues how was the performance and what were your fuel consumption figures like over the 1000 km trip? how far could you go on the sporty tank?was it consistant throughout the trip? i hope you can get it sorted. both my brother and myself have had a slow build rate lately,but as winter is round the bend we hope to have more time to get our projects mobile. bye for now,otto.

[Fiddler]

TFC

Glad your engine appears OK.
Its certainly a thought regarding the CVT and worth some consideration. I wouldnt have thought that the forces involved on a diesel bike would have been significantly worse with CVT that a trad set up though.
Im basing this on the low HP and low rpm compared to a snow mobile which rev hard and are significantly more powerful, although it is beyond what the engine would have been designed to handle.

Otto,

Performance is really hard to evaluate and describe without riding around with a petrol counterpart for comparison.
That said, it was pokey enough to keep in front of traffic away from lights(just) and had enough go for overtaking in normal traffic use.
It was geared for around 80mph top speed and would achieve it eventually in ideal conditions. It would happily cruise around 70 and find the rest with enough time.
I was thinking Petrol though when working out the gearing. It would have been better to gear the bike for 70 in the first place, have a much swifter bike betting there, and as this is well within the thoeretical top speed for the Hp, it would have always achieved it.
Nice as it is to claim your project bike does 80mph, whats the point if you need a runway to prove it

Fuel consumption varied over time with the bike, as I finished running the engine in and also as i learnt how to ride the bike properly. With CVT it doesnt matter how much throttle you give it with a diesel, its only ever going to accelerate as fast as the available HP and the drivetrain will allow. Also it is a weird sensation to continue accelerating with the engine at constant revs and takes some getting used too, without constantly wanting to twist the throttle more.
The last accurate figure on the return leg cruising at 60mph was 137mpg.
Total tank range could be worked out but I used to aim to fill up before the bike hit reserve. Here's a piece of blindingly obvious advice thats worth sharing with others doing builds, it caught me out so might others
When the tank runs onto reserve and you swop the fuel tap over, you may well have introduced air into the system and have a bleeding issue. Tempting as it is to run your fuel line and filters in a nice tidy unobtrusive run to the tank. It is far better to run them as near vertically A to B, fuel pump to tank as you can. It just might save you sitting at the side of the road turning your engine over for an eternity before it fires.

Cheers, Mark

[taildraggin]

Mark:

You've spurred some more thoughts about mounts. There is an advantage with your engine mounted CVT (unitized!), making rubberization somewhat easier. You will have to figure out how to allow the transmission cover to 'move' on it's rear mounts, or have it free floating back there.

Our constraint is the 4-corner industrial mount that we have to build around. They are in the wrong (vertical) 'plane'. Motorcycle mounts are horizontal.

I figure that the rubber isolation route has 2 paths: use the stock '4-corner' mounts by resting the engine on 4 hockey pucks or, build a rubber mounted subframe that moves the isolators to the vertical plane. (This would look, for example, like Sommer's or Altmann's bolt-on Enfield subframe with rubber isolators at the Enfield's original engine mounting points.)

The sticky bit is that the primary cover is bolted to the hard mounted gearbox - this all will need to 'move'.

Dry, open belt primary drives have a real advantage here, since you can leave the gearbox hard-mounted, with some sort of guard.

With the Enfield, we still have the issue of whether we are able to lose the engine as a frame stiffener (we probably shouldn't). With your looped Harley frame, stiffness won't be affected. (Your present mount is 'out-of-the-loop', too.)

Roundabout, you have a good candidate for rubberizing. I'd take a look into throwing some pucks under the engine using the original mounts and think about how to 'float' the primary belt cover or develop an different guard.

- Charlie

[d8veh]

Do you know about the system that Norton used on the commando, which basically rubber-mounted the engine, gearbox,primary drive and swinging arm as one unit. Perhaps a Commando frame would make a good donor for a Punsen, but I think maybe a little expensive. Otherwise the system could be copied in a custom frame.
http://ensanian.com/AE/NortonIsolastic.htm

[Diesel Dave]

If you need ideas how to rubber mount a diesel and gearbox then take a close look at Reinhards MZ conversions.

The engine and gearbox are hard bolted together as a unit and then rubber mounted to the swing arm pivot and frame spine - a brilliant concept copied directly from the original MZ.

The frame has the advantage of not having a downtube in the first place so all it's strength is in the heavy box section under the tank.

I know what my next conversion will copy;¬) they say it's the best form of flattery.

Dave

[taildraggin]

Yes, I've been staring at pix of the gearbox area of the Enfield to see if a engine/gearbox subframe can hung from rubber.

It is meddling with the stiffness provided by the engine/gearbox, though. I really hate snakey frames.

[arnaud]

Hi, since ido not know exactly how you engine was suspended, i do not kwno if this reaction will have a contributioanal value.
These chinese engines, like mine single, have a ground plate for mounting.
my engine has a subframe made for that.
Since these engines are designed to be as light as possible, the engine housing is, as you experienced, not suited for mounting.
My engine has, to reduce the (slight noticeable) high frequent vibration- but, since it is run in now, maybe it is totally absent- 2 supports(metal tubes, flattened at each side and hole drilled in) from the rear tank bolt to the 2 back corners of the cylinder head where's a sort of a solid mount..
Also, these two rods have a nick/bend in them(variates how off i drilled to holes to fit) and put a rubber washer between cylinder head and stud.
These factors make the studs to ABSORB the vibration present. in stead of let it knock both ways.
They work! every 6 months the tubes (12mm) tear at the knick's, showing they do their work! making new ones is 5 min. work..

I hope this gives you something to think about.
For the furure i'm planning a kubtota twin of the small 610cc V twin from kipor. (only when it is really smaller then the bigger ones, i haven't checked yet)

[Sphere]

OMG

They work! every 6 months the tubes (12mm) tear at the knick's, showing they do their work! making new ones is 5 min. work..

[Diesel Dave]

I use my teeth for that sort of thing

[taildraggin]

In her prime: http://www.youtube.com/watch?v=WxtGb1fS ... re=related

[Fiddler]

Guys,

Thanks to all for thoughts/suggestions on rubber mounting.

Its taken a while, but true to his word the supplier has sourced a replacement used engine, so things can start moving again.

Im now pretty certain that the engine has a weak point in the cases that the factory were aware off.
On the original engine, the crack originated at the point where the rear barrel meets the crank cases. A wedge shaped brace had been welded at this point. It was unclear to me if this was a repair or done at the factory.
Engine two also has a wedge shaped brace welded here, although its a different size and shape, odd since the serial numbers are near identical.
This may sound harsh but the evidence would suggest that the factory were aware of some weakess here and rather than redesign the cases, they took remedial action by adding a bit of bracing using off cuts of ali from the shop floor.
I think if was a matter of when and not if, one of these units failed here. Particularly if you are unlucky enough to get a bad shaker as mine was.


Taildraggin,
Cheers for posting the link. To be honest I'd pretty much lost the faith with Punsun. Seeing the bike move has given me an extra dose of motivation. Ta

[Dan J]

If only to hear that fantastic engine noise once again! Good luck Fiddler - hope you manage to get it sorted... Dan

[arnaud]

Good show. maybe try to get it more balanced??
And don't attach it to anything else than the ground plate