water pump or thermostat maybe????????

Hi All,
took the ‘HO’ out for its maiden voyage the other day and it did not go good. [:(]

After about 20kms, started with a slight tapping at a set of lights and looked down at my guage 'Holy crap NO OIL PRESSURE"
at about 2000 revs there was pressure and tapping wasn’t too much so rode it NICELY home, (hard for me to go easy on the exadurator (accelerator)) pulled up and switched her off and she spewed out coolant from cap behind fairing.

i am thinking thermostat could be stuck shut (bike was sitting for several years before i got it) which may have caused it to overheat and oil went thin losing pressure. temp guage was only half way.

i am going to check water pump and thermostat the first chance i get.

QUESTION;- would it be possible for coolant in oil to cause this, i think the engine maybe ‘making’ oil as in level getting higher, possibly from head gasket (may have caused symptoms), water pump or liner seal?

hi…downer[:(] that dosen’t sound too good, coolant in the oil can’t be helping anything, it could be that you have more than one issue going on. think you need to drain the oil off to see if coolant is getting into the oil.then start the bike with new oil, see if your oil pressure has returned,
exsessive pressure in the cooling system and coolant in the sump together would normally point to head gasket. im not sure if this could effect your oil pressure though as the oil to the heads travels up external pipes,
The water pump has two seals, one behind the impeller and one at the drive end with a external drain hole in between, i think you would see either oil or water dripping below the bike if either of these had failed.
think you’ve got a bit of investigating to do to pin point whats gone wrong

Coolant in your engine oil normally looks about the colour of white coffee, a caramel colour, the same for oil in coolant, does your oil and coolant look contaminated?

Oil colour isn’t too bad, actually looks a bit overheated more than anything and not too far up dip stick. I started the bike on Wednesday and oil pressure has returned to normal and ran fine. Now i am thinking possibly thermostat siezed shut and engine got that hot that the oil thined out causing oil pressure to drop.
I will pull thermostat and water pump and check both when i get a second. I might even pull the sump off and pressurise the radiators to see if water pump is bypassing or head gasket or cylinder liner, would these be visible with sump removed?
Taking note that this bike has been sitting around for about 10 years and everytime my brother worked on it he was either pissed or stoned. His heart is in the right place tho, his shed just burnt down with his 1979 CB900 and his 1984 GPZ1100.
everything burnt like my mum used to burn toast. he managed to save his XR600 and KX80 and i gave him my spare mig to give him a smile.
i hope he doesn’t ask for the VF back. He said he is going to buy a KTM990SM (powerhouse and fun ride)

Cheers all, will give update as soon as i get a chance to work on it.

See if you can borrow or hire a cooling system pressure tester. That will tell you if you have a cooling system problem.

Thanks Tony, was going to pressure test but first i want to pull thermostat and water pump to check for peace of mind, my brother came over last night and told me it was sitting for atleast 10 years hence I replaced both tyres for $250aud cheep for good quallity new rear and near new front still with nibs on it from south west motor cycle wreckers (the old rear tyre was down to 10psi and was still sliding and rock hard). when doing tyres I discovered I had oil leaking from right fork tube bottom bolt (fixed), rear caliper pistons had rust spots (caliper from same wreckers $50) replaced all brake pads, just waiting on new braded hoses to arrive, worked all weekend driving buses and going camping with my wife and kids on friday, so i will have to squeeze in ‘half an hour here half an hour there’. see how it goes.

Good luck with your diagnosis!

Yeh, thanks Tony, need to get it sorted soon incase i need to do head gaskets or something else like that.
Phillip Island for supers is creaping up fast (start of next year) WOOHOO [:D].

Sounds like you are making some good progress though, even though life gets in the way sometimes, LOL.
I think you are on the right track if it has sat for that long, seals go hard, gaskets dry out, tyres go hard (as you have already discovered) and you nearly need to remove all wheel bearings and steering head bearings and repack them with grease since it dries out over that period of time. Don’t forget your swing arm and prolink bearings too!

Yeh, i have checked most of that, bearings are all good in the head set, swing arm and wheels, need to get some new pistons for rear caliper from around the corner and then wait for braided lines and brakes are finished. going to try to finish work early today and rip the thermo i think. [:D]

Its all good, just like taking baby steps, it will come together HOPEFULLY in time.


Its well worth the wait,my beast took 8 months to rebuild the whole front end and silencers and tank and plastics
Lots of fun.
[:D][:D][:D]first time you open it up in a straight line and no fuzz about

Pulled thermo yesturday and she is fingered, only opened slightly in boiling water, so i cut the centre out and going to try it that way before i put a new one in her. oh yeh, I forgot, I still gotta check the sump if water drains from it, I am a dumb ass and will forget to shit one day. Brakes are done [:D][:D][:D] just need to get the ‘HO’ running right.


Hi Paul, how did you go without a thermostat? Did your oil pressure drop again?

havn’t had time to test run due to holidays with the family and very busy at work. gotta go to WaggaWagga for 3 days training. hopefully get time to give it a run on Monday (public holiday).


I was talking to a bloke on Saturday night and he said to screw spring off the thermo half a turn so it opens a bit earlier and keeps the engine a bit cooler, i did that to the other thermo I have and it looks good, opened earlier and opened wider, fitted the thermo, Drained oil and no water in sump. Fitted the braided lines and made a big differance, front lever and rear pedal only moves half way now.
Oil pressure drops still, thinking it maybe the oil pump or PRV. Could the PRV be getting jammed with gunk? I will remove exhaust and sump and check both when i get a chance. It is running at about 30PSI when cold but when it warms up a little it drops to nothing at idle. I wander if the oil mod i did would be causing it?

Old timers rule of thumb, 10psi oil pressure per thousand rpm, so at idle it will be low but should still be around 10psi and build from there. Check roughly in the following order, oil viscosity, oil filter, oil pressure switch, oil mod, oil pressure relief valve, oil pump and lastly and hopefully not the problem, main and conrod clearance.
Good luck Paul.
Tony Brown

Hay Tony, your advise is GOLD thanks mate, i have been doing some investigating and found out some things interesting - last night i took off the seat and tank and started it up, oil pressure on my oil mod guage read 40psi, as temp got warmer, oil pressure drops slowly until after a little while NOTHING. stopped the engine and removed the rear rocker cover and started it up again, i near got drowed in oil.
My conclution is this - my cheap ass oil mod did not work. the oil mod that every one gets takes oil from the centre after the oil filter where as mine takes oil from the outside before the filter. i used a sandwich plate designed to bypass the oil through a cooler, i knew that that would not work as i needed oil from both ports to the head, i drilled holes through the centre of the sandwich plate to get flow to ther filter but not filtering the oil before it goes to the heads. (i think as the oil gets hotter and thiner it takes the easy path straight to the heads. I NEED A PROPPER SANDWICH PLATE. yes i do feel like a bit of a dumb ass.
Does anyone have a spare sandwich plate for the filter from an old engine that they dont need and could part with for some aussie dollars? i cant afford the full kit and my oil lines, well, THEY WORK. any help or advise would be appreciated.

Did you manage to get oil pressure again? Glad you found the cause, and yes the oil will take the path of least resistance at every opportunity.
Don’t worry Paul, the only dumb-ass is the person who doesn’t try different ideas, who just follows other peoples ideas, I would have tried an oil cooler sandwich plate too if only I had thought of it, good investigative work in discovering the problem, after all we need to keep the grey muscle exercised as well.

Hi Tony, When the bike is cold i have oil pressure but only 40psi, it said in the manual it should be about 60-80 or something like that (it has been a while since i read it).
I still think if i put a proper sandwich plate in or modify mine, it should be goo. Anyone got a spare sandwich plate for the filter?Dropped my 1/4" ratchet onto the oil guage and cracked the glass, now that is leaking oil, have you seen the photos and do you think i should put a new guage on it or just plug it? any thoughts guys?

Hi All,

ITS DONE. [:D] [:D] [:D]

Got the plate for the oil mod back from the machine shop, drilled some holes, fitted it, started her up and got oil to the top end, put the rocker cover back on and the rest is history.
Took it for a small local run and when she warmed up had pressure at the guage at idle and she was running a lot happier.
Going to clock up some kms this weekend to Nowra, will have a better idea if she will make it to Phillip Island.
All i need to do now is go and see my mates at SouthWest and see if they have a set of cans i might be able to make fit as these are very rattley (actually sounds like a sowing machine), i think the guts are falling apart.
I have got a new oil guage on the way because the old one is cracked and leaking. for $35 it looks the part.

This “HO” of mine one day may actually earn a paint job and new HONDA stickers on the tank after all.