DT125R DTR DT125 Oil pump problem

[Dooooogster]

This has been a year long saga, but am not going to re-write war and peace here!

Oil Pump on DT has never worked. Took it off and found that the big cog inside the pump that connects to the drive shaft of the engine was burred and shredded. You could turn it by hand and the adjusting pump moves up and down fine. I have inspected the drive from the engine and it has no visible defects and when I turn the kick-start it turns fine - so no issue there. I put another oil pump on with a fresh cog, started the engine and that pump didn't work. Took it all off again only to find that cog stripped too (ruined another oil pump!).

So - 2 screws, make sure it is seated ok, nothing wrong with the engine drive shaft - so what is causing this to happen? Is it a bad design? Has this happened to anyone else? Or what am I doing wrong? None of the manuals say what to watch out for, or special instructions to seat the oil pump onto the drive shaft - it is just gently pushed on and 2 screws? I have another drive shaft, but it looks no different than the one currently on the bike. Have sourced yet another oil pump - but what is to stop it happening to this one?

Am I destined to premix two stroke in the tank from now on? Help!

[2 Wheels]

Firstly, can i see a picture of the worn cogs of the pump and the drive gear on the engine.

Dont know why its happening but might help to see what damage is happening.

[Dooooogster]

Firstly, can i see a picture of the worn cogs of the pump and the drive gear on the engine.

Dont know why its happening but might help to see what damage is happening.

Yeah, sure I can try to take a macro photo, but might be tricky to get the detail you are after. Will post when I can. You will hopefully see a cog inside the oil pump with the sharp end of the teeth all flattened and damaged, and a drive shaft (screw design) with no visible damage.

[jquinton]

All the teeth or some of, some of would suggest the oil pump side of things is jammed, all of them must I think be a meshing problem. Do you check the pump turns each step of instalation and do you turn the engine by hand to check it is seated correctly? Go slowly checking as yoy go and stop at the point it IS STARTING going wrong.

Hope its some help, other thing is a second pair of eyes watching as you go.

[2 Wheels]

Just had a we read of my manual, regarding your pump.

Like you have said it doesnt tell ya that much on how to refit the oil pump to the engine.

However ! things to check !

are you using the shims on reasembly, and a new gasket ? the shims are important so that each set of cogs line-up and connect correctly.

it also says when taking the pump off that ya might have to twist it a bit to disingage the cogs, so just make sure that they reconect fully and correctly when putting pump back on.

Is there any movement in the driveshaft comming from the engine, (up / down or left / right). there is a bearing here where the driveshaft exists the crankcase, although the manual says this is not likely to fail unless high miles have been done. How many miles on your bike ? If there is movement in the driveshaft then this would certinly eat the teath of the nylon cogs.

I am thinking that the prob is with the driveshaft and not really your pump.

Does it look like anyone has tampered with it or changed it to a different one for some stupid reason before you started working on it ?

I thing you shouldnt put the secondhand pump on till you find out for sure the driveshaft is REALLY working as it should be.

It is a straight forward system so it shouldnt be giving you all this greef.

Pics will be good if ya can get any.

[Dooooogster]

Thanks for taking the time to look into this 2 Wheels, much appreciated!

Took the side casing off tonight to look at the drive shaft - in case there was grim news within. Nothing untoward as far as I can see. There is in and out play, but this is the same as the engine casing I have on my workbench (I have 2 engines!) In addition the circlips (2 of) on the inside of the casing look like they are designed to have a bit of play on them (sounds strage I know). I was going to swap the casings over but as there was no difference and the drive shaft from the old engine looked in not as good condition, then I put the original back on with a new gasket. As for the shim there is a small washer on the end of the drive shaft. I also see that there is a rubber washer on the outer base of the drive shaft that doesn't seem to go too well with the oil pump gasket, so i will check if that should be there.

I am guessing I shall be far more careful putting the oil pump back on. I'll also test the new oil pump out on the old worktop engine first to see if there is a knack to it (and how to get it to engage)!

I'll look for the charger for my camera too (hopefully tomorrow!)

Thanks again.

[2 Wheels]

I wouldnt be happy with having a washer instead of the propper shims. For a start the pump will be able to rock on the washer,,,,whereas with the propper shims that cover the entire surface of the joining bits will be far more solid, therefor not letting your pump move and hence mabey not eating the teeth off the cog.

Then there is this,,,,how do you know that the washer is of the right thickness ? If it is to proud or to shallow this will mean that the cogs are not meshing correctly and hence eat off the nylon teeth in seconds when the engine is started. Are the Propper shims on your 2nd engine ?

That rubber washer should be there and as it doesnt seem to fit right with your gasket,,,,,,,,,,,,,is this because the washer (instead of shims) is to thick ???

That in and out movement you are describing should be fine as it is designed that way.

Aye, i think its a good idea to do a trial run on fitting the pump to your second engine,,,,see how it pans out.

If ya go ahead and fit the pump to your bike after this,,,,,dont start the engine,,,,take out the plug,,,,turn the engine slowley by the kicker and see if the pump is working corectly,,,,also try to listen if ya can here any tearing going on or any sign of resistance on the pump.

Thats all i can think of for the min.

ps. take your time !

[Dooooogster]

2 wheels, here are the photos - couldn't find charger so had to use phone -hope they come out ok.

You will see both oil pumps and their shredded oil pump cogs, the drive off the old engine - in same condition as drive shaft on bike, also the gasket, shim and rubber ring that came off the oil pump. Also included the bike -bought as a £200 basket case a year past April, now after about £1400 repairs (yes mental!) here it is.

[Vez]

2 wheels, here are the photos - couldn't find charger so had to use phone -hope they come out ok.

You will see both oil pumps and their shredded oil pump cogs, the drive off the old engine - in same condition as drive shaft on bike, also the gasket, shim and rubber ring that came off the oil pump. Also included the bike -bought as a £200 basket case a year past April, now after about £1400 repairs (yes mental!) here it is.

http://i983.photobuc...89/IMAG0134.jpg

http://i983.photobuc...89/IMAG0136.jpg

http://i983.photobuc...89/IMAG0131.jpg

http://i983.photobuc...89/IMAG0129.jpg

http://i983.photobuc...89/IMAG0138.jpg

Thought i would make it easier for people to see the pics.

[Dooooogster]

Cheers vez.

[2 Wheels]

Well mate, had a we look at them pics.

To me it looks like the cogs are not meshing togeather correctly. It looks like the drive shaft (screw type) comming from the engine is only barely catching the tips of the cogs in the pump. Hard to say why this is happening as the drive shaft has flanges that fit into the pump and hold it in only one position. So a question for ya,,,,do you know if there are different types of pumps for the different models (year) of bikes ??

However in your other pics i dont see any shims (or washer) like it showes in the manual, i only see the gasket and the two rubber o-rings. I still thing the shims are important to keep the right distance of the pump going on the shaft. If the pump can go in too far or not far enough then this will not let the two cogs line-up dead in the centre, therefor putting extra pressure (grinde) on eachother.

Have ya tryed the pump in the engine that ya have on the bench ??

EDIT: what thickness is this washer that is on the end of the drive shaft ?? it shouldnt really be there ! there should only be 1 shim and that is very THIN (i dont know of any washer that could be thin enough to match the shim).

[Vez]

Imo the o-ring is stopping the pump seating properly. My manual doesn't even mention an o-ring.

[Airhead]

Thats right, no o ring, the gasket does the job of sealing. Besides an o ring would normally have a machined out seat...not be squashed between two flat surfaces.

[Dooooogster]

Thanks for all the help by the way, will hopefully give something back to the forum when I build up my expertise! The little ring in my photo isn't rubber, it is metal and is number 4 in vez's exploded diagram. Do I need more of them? Also the rubber ring doesn't appear in anything I have seen or vez's diagram. At the moment I am pre-mixing with confidence and enjoying riding the bike without walking it home for the first time. It's great! Replacement oil pump arrived yesterday, although I will need to test it as the inner cog isn't rotating easily like the broken two. Am tempted just to suffer the oil light warning light and hassle of pre-mixing. Have got a tank of two stroke petrol to use up anyway. Lovely seeing the faint puffs of smoke coming out the exhaust. Although the purest in me wants the bike back to its original oil functioning design!

[Cynic]

Thanks for all the help by the way, will hopefully give something back to the forum when I build up my expertise! The little ring in my photo isn't rubber, it is metal and is number 4 in vez's exploded diagram. Do I need more of them? Also the rubber ring doesn't appear in anything I have seen or vez's diagram. At the moment I am pre-mixing with confidence and enjoying riding the bike without walking it home for the first time. It's great! Replacement oil pump arrived yesterday, although I will need to test it as the inner cog isn't rotating easily like the broken two. Am tempted just to suffer the oil light warning light and hassle of pre-mixing. Have got a tank of two stroke petrol to use up anyway. Lovely seeing the faint puffs of smoke coming out the exhaust. Although the purest in me wants the bike back to its original oil functioning design!

You say you have 2 engines, have you taken the drive shaft out of the spare and compared the 2. Do you have the pump on the other engine or did that die in the second test.

[Vez]

Thanks for all the help by the way, will hopefully give something back to the forum when I build up my expertise!

The little ring in my photo isn't rubber, it is metal and is number 4 in vez's exploded diagram. Do I need more of them?

1. If you rename the thread to: 'DT125R oil pump problems' then when ever anybody searches google for the same it will lead to this thread, and you will be contributing  .

2. I posted the second picture to show you that part no4 is slightly thicker than a shim, so no you don't need more then one.

Furthermore, If it was me, i would be taking the damaged pumps apart and examining them for any internal problems before fitting a new pump. This will also give the opportunity to measure the distance from the gasket face of the pump to the center of the cog in the pump, you can then do the same on the pump drive shaft to make sure they align and mesh correctly.

[2 Wheels]

As for the shim there is a small washer on the end of the drive shaft. I also see that there is a rubber washer on the outer base of the drive shaft that doesn't seem to go too well with the oil pump gasket, so i will check if that should be there.

The shim is the same shape as the gasket, it is a very thin piece of steel.

Aye, this rubber washer should NOT be there.

However in your other pics i dont see any shims (or washer) like it showes in the manual, i only see the gasket and the two rubber o-rings. I still thing the shims are important to keep the right distance of the pump going on the shaft. If the pump can go in too far or not far enough then this will not let the two cogs line-up dead in the centre, therefor putting extra pressure (grinde) on eachother.

Have ya tryed the pump in the engine that ya have on the bench ??

EDIT: what thickness is this washer that is on the end of the drive shaft ?? it shouldnt really be there ! there should only be 1 shim and that is very THIN (i dont know of any washer that could be thin enough to match the shim).

As it happens in your case i think the pump was NOT going in far enough and only catching the tips of the cog in the oil pump.

Imo the o-ring is stopping the pump seating properly. My manual doesn't even mention an o-ring.

Good pic there Vez,,,i agree,,,,the o-ring shouldnt be there.

Thats right, no o ring, the gasket does the job of sealing. Besides an o ring would normally have a machined out seat...not be squashed between two flat surfaces.

Yep,,,,agree with OG also.

Thanks for all the help by the way, will hopefully give something back to the forum when I build up my expertise! The little ring in my photo isn't rubber, it is metal and is number 4 in vez's exploded diagram. Do I need more of them? Also the rubber ring doesn't appear in anything I have seen or vez's diagram. At the moment I am pre-mixing with confidence and enjoying riding the bike without walking it home for the first time. It's great! Replacement oil pump arrived yesterday, although I will need to test it as the inner cog isn't rotating easily like the broken two. Am tempted just to suffer the oil light warning light and hassle of pre-mixing. Have got a tank of two stroke petrol to use up anyway. Lovely seeing the faint puffs of smoke coming out the exhaust. Although the purest in me wants the bike back to its original oil functioning design!

To answer the bit in blue in your post.

1) no ya dont need more of them.

2) the rubber ring---this is the shaft oil seal----it goes inside no.8 on Vez's diagram.

I was gettin a bit confused with some of your posts, but i think i have it now.

Putting the pump on----this is the sequence.

1) Put shim on the drive shaft------if ya have one.

2) followed by the gasket.

3) then put the small metal ring on the end of the drive shaft.

4) thats all that goes on it,,,,,,you are now ready to fit the pump.

5) wipe the shaft a bit with 2T to help putting on. Take your time and make sure the cogs are ligning up------if ya have to force it on then something is wrong.

Hope this should get ya sorted,,,,,,,after ya have freeded up the new Stuck pump.

[Airhead]

1. If you rename the thread to: 'DT125R oil pump problems' then when ever anybody searches google for the same it will lead to this thread, and you will be contributing  .

Done that.

[Dooooogster]

Thanks.

[Dooooogster]

Thanks.

Just as a footnote, the reason for all the trouble - started out an oil pump problem ended up a seized engine problem. Pretty self explanatory. Drive on the right is the correct oil pump drive for the DT125r, the drive on the left is the one that caused all the sheared cogs that led on and on and on........Not sure where it came from (tzr maybe?). Guess them are the risks when buyin 2nd hand bottom ends off the net.

Bike now going great only prob now is a little too smokie, so will have to add? some shims to the oil pump to decrease the oil flow.