KH 400 Oil Pump

[Tazman]

Good afternoon all. I'm nearing completion of the latest form of restoration of my KH400 and I'd be very grateful for your guidance. Despite my relative inexperience and general incompetence, I've managed to get it running. I can't however get oil through the pump and oil lines. I've followed the instructions in relation to bleeding etc and without result. I've cleaned the oil tank / filter and bled the air out of the feed pipe and purged it. I'm however a bit concerned about the flow through the pipe. It's more of a faint trickle (albeit constant) and I'm too ignorant to know if that's normal and whether or not the pump draws the oil from the tank as well as pumping it through the lines. Could anyone please offer any tips? Many thanks Paul

[Mitsui Spy]

Oil should really come out of the supply pipe at a fast-ish trickle, especially if the tank is over half full. The pump does suck oil from the tank so it shouldn't be a problem but it's worthwhile checking the filter gauze again and pulling the pipe off the bottom of the tank to see whether the restriction is in the pipe or the outlet. I assume the tank is suitably vented.

After that you're looking at the seals on the pump inlet and outlets, and after that the internal pump seals.

[Tazman]

Hi and many thanks for your response. The tank has been thoroughly cleaned out along with the filter and the feed pipe is new. To be fair I haven't looked at the flow directly from the tank outlet so I'll try that. I'll order a seal rebuild kit for the pump as which can't do any harm. I really appreciate your time and advice.

[Mitsui Spy]

Trickles are a bit subjective. One man's faint trickle may be another's fast-ish trickle
As long as it's coming out at a rate faster than the engine uses it, it's fine.

As a guide to how little the engine uses, consider 50 mpg at 50 mph at 50:1. That's a gallon of fuel used in an hour or 4.55 litres.
At 50:1 mix that's about 0.1 litres of oil used per hour (less than 2 ml per minute). Even if you double the fuel consumption and halve the ratio, it's still not much more than a teaspoon a minute so flow is very likely to be your problem as long as it's flowing.

These days fitting Dowty type sealing washers to the outlets seems to be a very popular update.

[Tazman]

Once again a huge thank you for the detailed response. If the flow is ok then I guess I'm looking at the pump, because there's nothing getting into the oil lines even with the lever wide open. As per your advice, I'll check the flow from the oil tank outlet rather than just the feed pipe and see what that looks like. I'm going to give the pump an overhaul as well and just make sure that everything is moving as it should. Hopefully I'll get to the bottom of it soon and thank you too for the heads up on the Dowty washers.

[Mitsui Spy]

BTW, does your tacho work?

[scouse]

I suspect your reusing the single use aluminium crush washers
If I was you I would fit dowty seals, I would use them on all the oil lines except the large side of the banjo bolt for the feed from the oil tank
I bought mine from earls performance products
https://www.earls.co.uk/

[Tazman]

Hi both and thank you again for the replies. Yes the tacho was working last time I checked. Thank you for the advice on the Dowty washers. I have fitted them pump side at the pump, but was worried fitting them to the main banjo bolts. I was concerned that they were too thick and may impede the inlet / outlet holes. Clearly not so I'll give them a go and many thanks again.

[Tazman]

Hello all and apologies but it's me again. So the rebuild kit has arrived for the pump and I've started stripping it down in order to access the seals etc. I thought I'd have a quick look on YouTube to see if there are any useful clips, especially as I'm far from being an expert. I came across the old Triple Darth clip showing a stripped down H2 pump. I appreciate it's a different beast, however many of the internals and principles look the same to me. From watching that I have a major concern. Along with everything else, he has the two part piston laid out and he states that it should 'simply push straight out' once other actions have been performed. Well sadly the one on my pump is effectively jammed in. It rotates freely when I turn the crankshaft arm (sorry if that's not the correct term) and I can see it move up and down. It won't however come out and I'm reluctant to force it. So, firstly would you know if it's not meant to come out of a KH pump and secondly, if this is a sign of it being knackered, are there any other pumps that are interchangeable with the KH? I ask because I've seen them available for KH250s and the S350 but rarely the 400. I'm just covering all of the bases here and once again any advice would be gratefully received.

[Mitsui Spy]

It is possible for all the parts to come out but there's no real reason to remove the plunger (the part that engages with the worm drive). It's very finely machined to be a precise fit in the housing similar to a hydraulic spool valve. It has no seals, it just relies on it's precision fit. When I've stripped pumps on their entirety in the past, mainly out of curiosity, I've noted that outside of their normal range of movement the plunger tends to bind in its hole and requires some light force to remove it. It's not a good idea to do so as the bore is easily damaged and the slightest bit of dirt will also cause it to bind. As long as it's turning freely and reciprocating, the pump should work. The only seals to replace are the various O-rings for the end caps and follower.

As far as I'm aware, the pump bodies and internals are the same across the S series, just the outer lever being different to compensate for the different amounts of throttle cable travel on the different models. Other than the 4 outlet pump I wouldn't be surprised if the H series ones weren't largely the same but I don't know for certain.

[Tazman]

Hi there and once again many thanks for your reply. Well I've tried just about everything I can now and still can't get any oil into and out of the pump. I've stripped it and replaced all of the seals without disturbing the plunger and everything seems to turn freely. I've checked the oil tank as you suggested and oil flows nicely from the supply nozzle. The filter is clean and undamaged. Still has the faintest of trickles out of the pipe at the pump end, but I've even taken these concerns to another level by using a different reservoir with a wider aperture and feed pipe. This I suspended directly above the pump so there were no issues with routing / air locks and after trying to bleed the pump with the cable lever wide open for some minutes, nothing. The only thing I haven't tried is testing the pump with a drill which I've read about somewhere. To be honest I'm now of a mind to buy another pump and try that, hence me asking if they're interchangeable. Again thank you for the advice on that one.

[Baff1960]

Hi.
I think you should go back to basics with this. These pumps are quite a simple design and incorrect or missing seals is the most common cause of lack of flow unless its blocked somewhere. Internal wear / damage should still produce some flow albeit reduced.
Remove the pump and double check all the seals are installed correctly. If all correct [ use a good reference ] look at other associated items that can affect flow - check the banjo bolts for blockages and correct flow through the cylinder supply lines with a bit of air for check valve operation.
Not sure how your running it but if its being tested on the bike take it off and use a drill to drive it [ correct rotation ] whilst connected to a slave oil tank which will ensure positive oil supply. You can use more revs to get better flow rates but be careful not to damage the pump drive. You should be able to identify the cause of the lack of flow and address.
Another pump could help but should be guaranteed working before purchase. S series pumps are more or less the same with different cable drive cams.

[Tazman]

Hello and many thanks for your time and the detailed information. I replaced all of the seals one at a time and as per the instructions. I was careful not to damage any in the process and all of the banjo bolts are free from blockages. I will certainly try the drill test but have no idea how to set up a check of the check valves using air. That is something I'll need to look into. Can I ask though. If it is the dreaded check valves, is it common for all three to stick / pack up at the same time and what could cause that? Many thanks again.

[Baff1960]

Hi.
Normally common faults with the a check valves is they are gummed up with old congealed oil or there's corrosion of the valve spring/seating ball. You can do a simple check by blowing in the end from the pump [ you can use your own puff, clean it first ] and feeling the flow at the cylinder end. Do it the other way and there should be no flow. This will prove you have a working valve. Checking the opening pressure [ about 4-5 psi I think ] requires an accurate pressure feed but as you want to check flow/operation it not relevant here.
If you have been checking it on the bike any flow through the cylinder feed pipes if the pumps working with the cam full opened will be indicated by air bubble pulses in the lines, slowly at tick over. Its impossible to assemble everything without some air. I've purged dry lines before on a running triple and seen each line purge in sequence in about 30/40 seconds at tick over.
Assuming that you have pre-lubed the internals with T2 don't run it too long if your unable to get flow. Use pre mix in the tank if in doubt, the worst about that is more smoke.
As I said before use a slave oil supply and run it with the feed lines off. If that doesn't work its a pump issue then investigate again.

[scouse]

Just out of curiosity how are you testing the oil pump?

[Tazman]

Hi and once again many thanks for your time with this. Ok so regarding the check valves, I can't get any passage of air through the lines when blowing into them from the pump end. I can however hear air coming through when I draw through the lines from cylinder end. It does require a fair bit of effort but of course I have no idea how hard this should be. If you think this is normal, I'll go ahead and check the pump off of the bike with the drill and slave tank. Can I please just check the following before I do? Lines connected at both ends or just at the pump? Correct rotation being clockwise? I'm sorry to be such a drain on your time / patience and thanks again in anticipation of your help.