Later Alloy Body Oil Pump in K0 Bomber

[AshimotoK0]

My understanding from  the Bomber experts on Hondatwins.net has always been  that fitting a later alloy body oil pump from a K2 onwards is the way to go to improve top-end lubrication.

However, I spoke with Jensen on the phone last night about various bike related subjects  and it seems that in his extensive testing of synthetic oils in the Bomber, he originally fitted a NOS CB500T pump but experienced wear and reverted back to the steel body one. I will ask him to comment specifically on this but meanwhile I went through his posts and pulled out some pertinent points and copied them into the attached document. He certainly is a fountain of knowledge on the CB450 DOHC and CB72/77.

I bought a later alloy body oil pump, used but good condtion, for my K0 and passed on a NOS steel body one that  I was offered fairly cheap ..  I think I will contact the guy again and see if he still has it 'just in case'.  Jensen told me that there were several modifications to the K0 pump. I suspect that the one I was offered was an upgraded part as it came from Honda's Service Centre that was in Nottingham in the 60's/early '70's.


https://www.dropbox.com/s/kb8pbuwl3a4jdxv/jensen.doc?dl=0

[MrDavo]

I’m not sure where this leaves me, Ashley rang me about it while I was on to of a French Alp, skiing, as Jensen had given him the impression that some modification may be necessary to fit the later pump. I am now in Chambery airport waiting for our delayed flight home.

My 450 is a K1, it did have the early steel bodied pump, and I have fitted a later 500T pump to get more pressure, I’ve read a few threads about it.

The pump I fitted was from a low mileage bike, and doesn’t (yet) have a worn alloy body. I don’t think I have a clearance issue though, as mine is a five speed engine, reading Jensen’s document the problem arises when you fit the late pump with the four speed clutch.

I’ve kept the original steel body pump, I can always switch back.

Perhaps Jensen can comment if he sees this, I don’t want to pull my engine apart again if I don’t have to.

[K2-K6]

Mr Davo,  off topic but we, yesterday, drove back past Chambery airport from the alps leaving Les Arcs in the morning to return UK.
Brilliant snow this year, some of the best for a long time. Where did you stay?

Back on topic,  some of the metallurgy in these areas can be the inverse of what would appear logical in wear patterns. A steel component may be worn by a softer material given the right circumstances. The cam lobes, also,  are lubricated in a zero pressure environment,  so increasing pump pressure will not improve local were rates. That specific point needs absolute flow to clear used / heated oil and replace with supply as fast as possible.
Pump pressure is similar to resistance in electronics,  I believe. The system will need lowered viscosity to get more supply,  only then would more pump capacity give a relevant increase in oil supply to the cam lobes.

Nigel.

[AshimotoK0]

I sent Jensen a Facebook message and sure he will respond in due course.  he's been away on business so it may take him a couple of days to respond.

I read somewhere on HondaTwins that there was an official Honda Service Bulletin on the early pump. Someone had posted an image of it but it was Photobucket and no longer visible in the post. I will investigate further. The construction of the alloy body later pump is the same as the CB250/350K's  so I will have about half a dozen of them that  I can inspect. I think am going to grab the NOS steel body one if it's still available though.

[jensen]

Hi, took a while to respond, but better late than not at all......

The intresting part is the spacer, which is't a standard one, it's thinner. I will find the pump somewhere in my stash and measure the parts... I will also make a better picture of the install guide as soon as I have the time.

btw, happy easter everyone !

Pictures :

[MrDavo]

So unless someone can find me that thrust washer (Google can’t) I need to put the old oil pump back, which means dropping the oil, and  taking the clutch and oil filter off again.

Feck.

[jensen]

I don't think it's difficult to make such a thrust washer...

[AshimotoK0]

Thanks Jensen... Mr Davo's bike is a '69 K1 CL... is the thrust washer change  still applicable to 5-speed bikes?

When I pickup the NOS steel body oil pump this week, I will quiz the guy to see if he has any Service Bulletins pertaining to the CB450K0 ...if anyone has them it will be him 

[K2-K6]

http://www.hondarestoration.com/for_sale_motoqs.asp?m=Motorcycle%20Parts&p=Parts%20and%20Accessories&c=10063&k=CL450

I haven't time at the moment to look through here,  but there's alsort of related parts.

May by worth a look through.

Nigel.

[MrDavo]

It looks like a matter of alignment, if the kit is for a K0 four speeder that would explain why Jensen got uneven wear without it.

However if it’s for any engine swapping a steel bodied pump for an alloy one, i may well need the thrust washer, even though mine is five speed, it depends on whether the washer compensates for the body being on a different alignment or something that changed between the four and five speed clutch.

It may be easy for you to make, Jensen, but not for me without a lathe. If I had the exact dimensions I’m sure I could pay someone to make it though, if I had to.

[AshimotoK0]

How many miles has your K1 done Dave? From the looks of your strip-down, the cams & rockers looked pretty damn good to me (apart from the PO careless damage to the  damper ring flanges)  .. So IMHO it may be better to put the old pump back and let the bike warm up on idle and it will be good for many more miles. If you can wait till the end of the week I am visiting the guy with the NOS oil pump and he may well have a Service Bulletin on the early oil pumps. He got most of the stuff from the long gone Honda Service dept. that was in Nottingham when the bikes were new.  I can also compare the NOS  oil pump to an early bomber one ..it may well be that they modified the design slightly.

[jensen]

This is the earliest one, fitted in my bomber, look to it closely and you'll understand why all the early bikes having camshafts and rockers damaged....
The modification was simple, but took a lot of work, the whole pump had to be disassembled. Some dealers however didn't, and just rotated the screen 90 degrees. A handy person can do that without disassemble the pomp.

[AshimotoK0]

If anyone wants a NOS filter  screen sealed in bag I have a couple at £12 ea plus  £1.50 UK post.  DS charges £45 special order.

[ Guests cannot view attachments ]

[MrDavo]

I’d like to have the 30% extra flow from the later pump if I can, just for peace of mind.

Last night I read all the posts on the twins forum that Google could find about oil pump upgrades, the consensus from those that had done it with no problems was to use the conrod from the original pump, as there were small differences at the ‘big end’, but fitted with the steel piston from the new pump. That way the dimensions at the clutch end are perfect, but the action is exactly the same.

I’m going to pull it apart and have a good look and a measure, as I have been turning the engine over on the starter to get oil pressure I’ll look for any damage from misalignment.

The upside is that my kickstart return spring is pathetic, I’ll take the opportunity to fit a new one from CMS.

[K2-K6]

I wondered what this one is?  As it seems to have a different alignment to others.
https://www.ebay.com/itm/71-Honda-CL450-Oil-Pump/270370216947?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20150313114020%26meid%3Dbc7d28487f4b40b3922a637ec8e6e992%26pid%3D100338%26rk%3D17%26rkt%3D30%26sd%3D142564278298%26itm%3D270370216947&_trksid=p2141725.c100338.m3726

[ Guests cannot view attachments ]

Appears to make an attempt to alter the sideways loading on the oil plunger.