RUMCars Forum
General Category => Unusual Microcar Discussion => Topic started by: Bob Purton on May 05, 2011, 02:47:39 PM
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Hi all. I'm told that Isetta's are prone to dropping valves if driven fast for prolonged periods, does anyone have experience of this? How about Heinkels? If so whats the solutuion? Stainless valves? Any suggestions?
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never heard of it in Heinkels. I certainly never had a problem - me and my mate mike simmonds used to ride them very hard too.
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The valves on Isetta - possibly more so on British, take advice - featured some that were made of a head and a stem welded together. These suffer fatigue to the rear of the weld as the metal is stressed. A build up of crude on the valve stem can be a cause, over revving also will promote fracture, but often times the valve actually fails at low revs from metal fatigue. The head simply parts from the stem and drops onto the piston. Normally this cause quite catastrophic damage to the top end which can be cleaned up and piston replaced. It has been known to end with the spontaneous random dismantling of a previously good engine for no apparent reason with cylinder in half, crank bugnered, head chewed and so on making the majority of the unit scrap. It has been, I believe, identified which valves were the main problem and it is good sense to replace them with a better manufactured item either spun welded or one piece, I assume. I do not think these are expensive. Certainly for the price a worthwhile investment if there is any doubt about Isetta valve condition.
Trienkels are far less prone to dropping valves but it is not unknown. I think the frequency is within acceptable bounds and in fact I have seen more failure of the ali loops that hold the valve rocker bearing shafts in than actual dropped valves. The Heinkel engine runs twin springs to the Isetta's, I believe, single so if a spring should fail - not heard of one that has - the second will salvage the situation as the engine will see a drop in performance leading most folk to find out what happened before an expensive failure. Again take advice as to Isetta valve spring failure or not from someone who knows more than me. Again crud can get deposited on the valve stem and it is advisable to clean it off before it interferes with the valve stem. This was offered as a principle reason for valve failure back in the day on any of these types of engine. Heinkel engines actually like revs, within reason, and despite the racket that sounds like the unit trying to get through the bulk head and sit next to you it is actually better to use the revs than hang on the superb torque such a small unit can give. Not least because as a splash fed crank it needs revs to get oil and cooling air about. Slow running means poor oil feed and early failure from heat and faster wear from poor lubrication. A situation not aided by many owners insisting on running the incorrect oil grades! The Isetta has an oil pump and is perhaps driven with less revs relying on its larger cc to make progress though clearly some enthusiasm is needed to get the air blowing round the cylinder. On running at high revs the problem with the Heinkel engine is the long ali pushrods. They can deform(?) or otherwise jump out of their cups at each end, possible due to valve bounce. At the bottom this can lead to the cam follower/rocker arm snapping in half, it is not very strong across its shaft because it does not have to be when all is in place. At the top the shaft can be jammed into the rocker arm. Either way your not going anywhere. It is possible to get home on a bust ali loop though. I have done so by inserting a large screwdriver through the oil filler (big one in this instance) and levered the rocker back into place. As long as tension was kept on the lever the car drove as normal.
Trust this is of help, interested to hear others suggestions/factoids/critic as I am not an engineer, this is roadside wisdom, its less accurate cousin.
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Thanks Al. This kind of backs up what I have heard except for the fact that Isetta's also have inner and outer valve springs so I think you got that bit wrong. Could it be your Isettaphobia kicking in? :D Now I need someone to tell me where I can get top notch replacement valves.
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My old bufty mechanic pal told me years ago, that the valve wears where thecollits locate (how do you spell collit / collet??). Instead of a nice 90 degree recess where the collit locates, it becomes rounded after 15k miles, causing the collet to part company with the valve at high revs...then BANG...........
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Hi, back home and now with one working car- Scenic!! garage cleared all logged faults from ECU and it runs as new (so far)
I was told to not even start an engine unless certain the valves hs been changed to stainless one piece ones. I too had thought that the early valves were friction welded two piecers. Of course dealer spare part stock items could mean that folk were still fitting them well after design changes.
I had another related fault that showed itself as oil all over the engine and engine compartment, tried lots of solutions in the end it turned out to be a loose valve guide. So machine shop engineer and oversize guides fitted I think this invloved freezing the guides and heating the head??? I had fitted stainless valves and the hole in the guide was OK that was what threw me I did not expect the guide itself to be loose as this only happened when the head got hot.
Just a related ramble look forward to more views to keep them rolling rolling rolling (horizontally only)
Good luck-- it will be running better than new before long!
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Hi Ian. Glad to hear the scenic is working again. Where did you get your stainless valves from? She is running good but I just want to go over a few things in preparation for some longer runs this summer.
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Dear Bib
My old Bufty mechanic Pal, Bryan, said to me once, ( listen very carefuly) that labouring and over reving the isetta engine were the main causes of engine failure. Provided you use the gears and keep the engine singing, then they should last. So it is how you drive the car that is the issue.
Chros Thimus
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Thanks Al. This kind of backs up what I have heard except for the fact that Isetta's also have inner and outer valve springs so I think you got that bit wrong. Could it be your Isettaphobia kicking in? :D Now I need someone to tell me where I can get top notch replacement valves.
Ah, it is many a year since I looked at the internals of an Isetta engine.
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Hi Chros Timus, Bib hear! Thonks for that advis, I'm nit a fist drivor so shod be ik! Have you been drinking?
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Hi all. I'm told that Isetta's are prone to dropping valves if driven fast for prolonged periods, does anyone have experience of this? How about Heinkels? If so whats the solutuion? Stainless valves? Any suggestions?
If I'm right, my Dad had that in his old Tiger! I know that the piston had a hole in it, my dad justput a screwdriver through the spark plug hole, and was suprised about the screwdriver just "falling in"! Luckily he got it running again, a friend brought a spare engine, and he fixed it at home.
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Dont understand, Jonathan, tigers dont have valves.
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back in relative comfort zone with Isetta
The IOCGB have them in stock and the 'new' new spares man is operational from May1
based near Milton Keynes stuff should be on IOCGB web site or if difficulty let me know and I will try to find details.
I am not on the committee!!! as I do not work well on them--but have good friend who is.
All so far written is what was passed on to me too. Not to labour or over rev the motor.
Marks on speedo for gear change good guide
1000mile oil changes and the engines are alleged to be bullet proof
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Dont understand, Jonathan, tigers dont have valves.
Unless it was one of the re-engined Tigers which used to do the rounds yonks ago. Don't forget, old Nick's been involved with a fair few in his time. :)
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Ah yes! Maybe it was that mini powerd one he had.
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Hello, This is old Nick here. Yes, I've had a few Tigers, five over the years. Still got one in bits. Jonathan is getting mixed up with the melted piston I had on the Tiger on the way to Scotland some years ago. It was a proper Tiger motor. I have had a valve drop in my Isetta back in 1980. You can get decent valves from Germany these days. Nick.
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Ah yes! Maybe it was that mini powerd one he had.
Well, there it is, my dad corrected me, the spark was at the wrong time, so heated up the piston a tad too much. He still has the mini engined TG500, just that hes turning it back to a normal TG500 now, hes gonna do it turquoise. Its in the garage still, in bits!
My dad said I can probably restore the Velorex, when I have spare time after the Nobel, it will be quite fun. Yes, I know, I like projects ;)
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And the MIni bit of the MIni engined Tiger is being turned into - well I guess a Mini engined Messerschmitt that looks like the MIni engined Tiger as it was after it was converted from a Tiger to MIni power, and all this in Norway to replicate a car from Switzerland last driven in Britain and now in France. International Bubbling can be confusing!
Velorex are bonkers and assuming the skins are in good condition, great fun. You could 'customise' it with special skins though. I rather liked the idea of clear skins, see everything with cilia like flowing lights down the side. A giant paracetium (spelling) or such. A Gatso speeding ticket would be of a guy sat in some scaffolding with a big grin. Maybe grinning is chargeable these days.
There you are Nick. We used to be the 'young' blades in the scene. Now your 'old' Nick and I am probobly something worse! I think I need a Bentley.