450/500T Startup

[AshimotoK0]

I got this from the new Vintage Honda Twins site from the 450K1 User handbook.

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[MrDavo]

Interesting they are suggesting at the top of the page that you give it a few kicks with fuel and choke first, I’ve never done that.

The warmup makes sense, as it takes an age for oil to get up to the exhaust cam.

[K2-K6]

For the manual text you've highlighted Ash, it looks as if they have lost some nuance in translation.

To me it means a fast idle by the first passage,  with the second warning against a thrashing while outputing maximum torque. The two I feel are very different conditions for an engine.

Realistically, a cold start will always involve compromise in pure technical terms.  In trying to normalize tokerances as heat comes up while attempting to keep the lightest load on the disparate collection of components will ordinarily place some risk in the event. 
A fast (elevated) idle speed while running the least amount of fuel enrichment is the best route in my view. 

Revs as an absolute are not the risk that's often projected,  if compared to running rich on choke to keep it going at lowest revs while blipping it are ultimately far more detrimental,  especially to the oil's condition as it very quickly dilutes with unburnt fuel byproduct.  That of course will compromise the total lubrication all the period during which the engine is run.

The oil supply is ultimately linked to the crankshaft revolutions,  making the cycles the cam experiences prior to full oil delivery mostly the same and  not time dependent. 

It doesn't look like camshaft wear comes from start routine though,  most engines are broadly the same in crankshaft favoured primary oil supply building pressure first,  subsequently the ancillary components follow. 

[the-chauffeur]

Ash - I've just found an old thread where you were pondering a roller bearing conversion on a 350 engine.  Did you ever get anywhere with it?

I'm asking because I'm considering going the Cappellini route with a 450.  I'm a little paranoid about the fragility of the exhaust cam and so along with the conversion kit I'm thinking about adding the oil filter kit, oil line and bored out/bigger oil pump piston mod.  Yes, that's probably overkill for a road bike, and yeah I've probably got more money than sense . . . but given the lack of liquid cooling in the 450, I don't like riding in modern day city traffic on a bike designed for 1960's roads because of the stop/start nature of the journeys I do.  I want to keep heat to a minimum and I suspect the rollers will help.

K2-K6 - would the fact that the 450 cams are suspended at height with no access to oil until it's forced round by the pump make any difference to lobe wear from start-up?  In the case of the nearside exhaust lobe, received wisdom is that it can take anything up to 90 seconds for oil to get to that point from cold (I have no idea how true that claim is).  Given the oil will also be at its thickest when cold and that's likely to reduce its spray coverage, that's gotta be tough on that lobe. 

It's not a phenomenon that seems to happen much in other similar bikes and I'm wondering whether that's because most have oil baths immediately below the cam lobes that offer even very small amounts of lubrication until oil starts being pumped/sprayed about.  Couple that with your theory about oil condition/contamination and I guess it's easy to see why the 450 exhaust cams fail so regularly. 

[AshimotoK0]

Ash - I've just found an old thread where you were pondering a roller bearing conversion on a 350 engine.  Did you ever get anywhere with it?

I'm asking because I'm considering going the Cappellini route with a 450.  I'm a little paranoid about the fragility of the exhaust cam and so along with the conversion kit I'm thinking about adding the oil filter kit, oil line and bored out/bigger oil pump piston mod.  Yes, that's probably overkill for a road bike, and yeah I've probably got more money than sense . . . but given the lack of liquid cooling in the 450, I don't like riding in modern day city traffic on a bike designed for 1960's roads because of the stop/start nature of the journeys I do.  I want to keep heat to a minimum and I suspect the rollers will help.

K2-K6 - would the fact that the 450 cams are suspended at height with no access to oil until it's forced round by the pump make any difference to lobe wear from start-up?  In the case of the nearside exhaust lobe, received wisdom is that it can take anything up to 90 seconds for oil to get to that point from cold (I have no idea how true that claim is).  Given the oil will also be at its thickest when cold and that's likely to reduce its spray coverage, that's gotta be tough on that lobe. 

It's not a phenomenon that seems to happen much in other similar bikes and I'm wondering whether that's because most have oil baths immediately below the cam lobes that offer even very small amounts of lubrication until oil starts being pumped/sprayed about.  Couple that with your theory about oil condition/contamination and I guess it's easy to see why the 450 exhaust cams fail so regularly.

Sorry I  missed this last reply.  The needle roller conversion was for a CB250/350K. I bought all of the bits but then acquired a stash of decent standard cam bearings so I sold all of the conversion  parts to Pacre Racing...or for his mate anyway ...... remember him? Used to build Honda engines and sell parts until his place burned down and I think he's a pro. ballroom dancer now or something now 

I think the best thing Capellini does for the cam problem is a re-designed baffle plate which somehow improves the oil retention in the area of the exhaust cam that's problematic. HondaTwins.net is pretty defunct now but there is a new forum called Vintage Honda twins and I am pretty sure a member there (ex-HondaTwins.net)  has made his own version of what Cappelli does. cappellini one is expensive for what it is. I will try to find link of the forum guy who made his own.

http://www.cappellinimoto.it/catalog/motorbike/CL450/product/200
http://www.cappellinimoto.it/catalog/motorbike/CL450/product/201

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[the-chauffeur]

No worries.

I'm pretty sure it's Tom (AncientDad) over at the VHT forum who made his own - either that or he linked to the thread where that was discussed at a time when the HT forum search function still worked

I ended up buying one of the Cappellini baffle plates a while back.  Nicely finished but not cheap for what it is (and the fact that the UK importer is pretty much hopeless doesn't help).  As I've found out more recently, they're very sensitive to placement - I've managed to shave down one of the edges because the plate was fractionally to close to the side of one of the cam lobes.  Trouble is, it's virtually impossible to see whether it's fitted correctly - you've just gotta put it in place and sort-of hope for the best.

I've kinda gone off the idea of the bearings for now.  Can't remember the reason off the top of my head but it's something to do with the machining down of the journal ends.  Might end up going for one of the oversized standard oil pumps at some point, but right now I'm more concerned with trying to iron out fuelling issues following a Mikuni carb swap.

[K2-K6]

"K2-K6 - would the fact that the 450 cams are suspended at height with no access to oil until it's forced round by the pump make any difference to lobe wear from start-up?  In the case of the nearside exhaust lobe, received wisdom is that it can take anything up to 90 seconds for oil to get to that point from cold (I have no idea how true that claim is).  Given the oil will also be at its thickest when cold and that's likely to reduce its spray coverage, that's gotta be tough on that lobe."

I feel that this overall assessment appears more of an "assumption" within the community that run these engines.  Certainly it would be foolish for me to claim that less oil for anything like this could improve longevity,  but it just doesn't appear to be the root cause of failure,  time of supply,  that is. If you run many engines with covers removed to see cam supply I think you'd be surprised at the time it takes to fully establish significant oil level to these components. 

Diluted oil,  certainly,  that's simply making a reduction of both film strength (principle requirement here) and will ultimately give reduction in oil pressure (affecting pressure fed areas and components) also to drain away from top of engine faster than design intended. Of course, the speed it drains from pressure controlled areas affects how long it takes to arrive at the furthest extremities too. To me, dilution is all undesirable.

I'd question the logic of increased pump size as the system pressure ultimately controls the flow when considered at the oil viscosity that you pump.  The excess has to be dumped via the pressure relief valve,  and so does nothing to improve the supply. Think Jensen has data for this on twins forum. The pressure relief valve is after all there to save the oil pump drive on any engine.  I don't see any gain,  just more delivery and more blown out the valve.

The simple answer to viscosity at lowered temps is to reduce the "w" number specification on oil used as that ultimately controls the speed at wich the oil travels within a system at standard specification.  A 0W/30 would do this, which is not as many would interpret  but it would reduce the cold viscosity and simply arrive at destination faster.

The true cause of the cam wear on these appears to originate with exhsust cam clearance. Again,  Jensen has some very accurate record of what happens here.  I believe he has that correct.  When you compare the observation about oil arrival time in seconds to the amount of seconds of engine run time,  well it's actually a minute segment proportionally. The characteristic of how the clearance is adjusted in this design appears to remove any wear items that would at least mitigate valve seat wear. In other words, a virtually perfect engineering concept,  or close to it. The valve,  in moving toward the operating mechanism simply removes the tolerances it needs,  again Jensen's data would seem to prove this.  That will ultimately compromise any valve gear system, ie. Losing clearance as it destroys oil film for literally every rotation the cam completes.  Jensen watches those clearance like a hawk and I believe that's the answer.

[SeanFD]

The characteristic of how the clearance is adjusted in this design appears to remove any wear items that would at least mitigate valve seat wear. In other words, a virtually perfect engineering concept,  or close to it. The valve,  in moving toward the operating mechanism simply removes the tolerances it needs,  again Jensen's data would seem to prove this.  That will ultimately compromise any valve gear system, ie. Losing clearance as it destroys oil film for literally every rotation the cam completes.  Jensen watches those clearance like a hawk and I believe that's the answer.

I followed what you were saying up to this point. If I get you right, you are saying that the valve (stem, seat. what?) simply wears the other components (combustion chamber seat, guide, small rocker pad?) to the size and shape it needs and in order to do so removes any oil that gets in the way, thus reducing lubrication and increasing wear?

I have just spent several weeks trying to sort out the top end on a 450K1 which was lacking compression https://www.vintagehondatwins.com/forums/showthread.php?2045-Dry-Cam-Chain-and-Rockers! without success because one of the valves is bent.

I read quite a bit about wear and tear of the cams and rockers and would therefore like to understand the process.

[taysidedragon]

I don't know these engines, but I assume they don't have an oil bath like the 400f.
That holds some oil in the top end and as soon as the camshaft rotates it dips into the bath and picks up some lubrication until the cavalry arrives from the oil pump.
Is there any way of modifying the 450 head to hold some oil for the cam?

[Skoti]

Gareth,

I'm don't know those engines either, but would the 'oil flow conveyor, exhaust camshaft'  pictured earlier in this thread be the answer?

[taysidedragon]

Gareth,

I'm don't know those engines either, but would the 'oil flow conveyor, exhaust camshaft'  pictured earlier in this thread be the answer?

Yep. I didn't see that. 🙄

[K2-K6]

Yes I can see what I've written is a bit clunky  if I separate out the above to give each element clear air.

Common to all camshaft and follower surfaces,  the gap when not lifting is THE most crucial aspect of lubrication as it takes oil round the cam and refreshes the oil film on the rocker surface ready for the next load phase as it comes to lift the valve.  Losing that clearance will usually destroy any cam and lifter arrangements.

If the design of the valve train is very concise such that it stays, when set, extremely accurate, then this part of the train is unlikely to change it's clearance.

Valve sealing face along with the valve seat (particularly after rebuilding) are the area that will ordinarily show the most change during use.  This effectively moves the valve into the head and closes the gap set by the tappet.  Ultimately this compromises the oil film as above, and usually unheared in running. Setting the initial gap to the largest tolerance and very carefully checking at intervals will avoid this scenario.  My reference to Jensen is because he has recognized and recorded this process through his building and running these engines to a very highly resolved level.  The valve clearances very slowly close until it seems they are fully established, then staying fairly constant over more miles.

I think it's a foible that we usually respond to valve clatter in the desire to go and check clearance, but the obove is the real risk and will pass completely unheard, until something obvious fails.

Hopefully this expansion makes clearer than original.

[SeanFD]

Ah!

Got it now thanks. And I can now see the reasoning behind the thought that more wear/damage will occur during running than at start up.

However the start-up theory would seem to explain the greater wear on the left lobe/follower, though not, to me at any rate, why the exhaust suffers more than the inlet.

[MrDavo]

I’ve seen CB 450/500 based race bikes with an oil feed straight from the oil filter cover to the top end.

Not pretty but you can see why they do it, it shortcuts what’s just a longwinded route for oil that feeds the top end. On the other hand, a race bike is all about going full bananas when everything’s hot, rather than worry about what happens when you start from cold, so did they just find the feed inadequate?

Edit: I found an example, albeit the feed goes via an oil cooler, including back in to the bottom end.

[royhall]

Any idea what feeds the left hand side in that photo?

My experience with the oil system on these engines is problems with the oil pump. On the K0 engine there is no way to tell what the oil pressure is (or isn't) as no red warning light exists nor a pressure gauge or even a simple button as per a Triumph. When building mine I managed to get hold of a NOS K0 oil pump, at the time I also had 3 used items. The new pump was fairly tight tolerences and quite stiff to move whereas the 3 used pumps were loose and sloppy. As it's a recipricating pump that sloppiness will loose pump pressure. Fitting the later model pump on an early engine does not work as the piston is a larger diameter which effectively moves the operating arm over by half the diameter difference. It will fit but the offset applies sideways force to the piston and wears it out.

After building my engine I filled it with oil and ran it with the starter motor on the bench with the cam covers off and plugs out. It took a while on the very first run to fill the centrifugal filter and oil galleries. All runs after that produced a good supply of oil which arrived at the inlet cam within seconds with oil at the exhast cam a few seconds later. I wish I could compare those bench runs to an engine with an old sloppy pump fitted. I think the pump is at least the partial culprit here. A pressure gauge would be an ideal defense.