Too rich jetting can wash oil injection film away?

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Vintageman
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Too rich jetting can wash oil injection film away?

Post by Vintageman »

EVer have something like this happen to you?

New fresh board top end and done to spec (checked it), New oil pump which I primed by removing clutch side cover and drill running pump gear. The oil lines were pumping equal and full, no air. Good crank which had only 5500 mile no rust, checked it for true in lath centers and very little side shake.

Here is my screw up, I think, I decided to try early style air box GT250L on a GT250A. The L has 112.5 round mains and the A is 92.5. Also L has 26mm carb and A has 28mm carb. So I started with 115 mains.

115 too rich (Plug fouled @~WOT)
112.5 too rich (Plug fouled @~WOT)
110. 00 too rich (Plug fouled @`WOT)
107.5 too rich (Plug fouled @~WOT)
105 too rich. (Plug fouled @~WOT)

Scrapped that Idea and put on stock GT250 Air box a 90 main was OK with chambers (just like it was before I did this foolish thing)

I probably had 150 Miles on this jetting attempted and 100 on top end before that

At the end of this fiasco, engine was making a lot of noise and low compression (125 PSI was 150 psi relative to my gauge at least).

Torn it down and the rings were almost half worn the pin overlap part was almost gone… 100 thou gap! , even cylinder had ridge on top, deeper wear near transfers since less wall area there… :shock: mess.

Pistons looked OK comparably :wth: .

I had started with some oil in gas, but removed since thought it was fouling plugs,

I guess what has happened is too rich fuel had washed away the oil provided by injection system.

Does that make sense to you? It seam if true could have happened to those trying pods.

I wish I left a mix of oil in gas. In hindsight the plugs fouled with charcoal like black soot not oily black
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Re: Too rich jetting can wash oil injection film away?

Post by pearljam724 »

I've read many times that guys are darn near using the same jetting with expansion chambers and pods, as they would with the stock air filter and stock exhaust. Just a tad richer is where they are running best. The reason for that is, most likely they and yourself have bought cheap pods. Cheap pods don't suck that much more intake than a stock air filter. Most people tend to think because they are pods, they will need a much richer jetting. That's only the case with a well known brand pod. You get what you pay for in regards to them. A good example is all of the Hong Kong or China ones often bought from Ebay. Knowing this, is one of a couple reasons why I don't like pods. Because, Im not about to pay a large price for good ones. When anyone can accomplish the same exact performance from a stock air filter. If the jetting is correct. Any aftermarket filter will only yield a 1-2 hp gain at best. Which is not noticeable the slightest from the seat of your pants. So, I see no need. Unless someone has a rotted or missing air box.
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Re: Too rich jetting can wash oil injection film away?

Post by Vintageman »

Thought my first post was clear? I'll clarify: I did not use pods. I used OEM Air intake setup from earlier model 74 GT250(actually box is a T350), just like early GT250, but air box inlets tubes are a little larger, new filter in it too) Just early OEM versus Late OEM Air intake main jetting difference (only main is different too) .

But my point is not about pods.

Has anybody run too rich fuel and oil injection only and had this happen (ring/cyclinder wear fast)? I have a lot more years of experience/foolishness with 1970s/80s sleds or MX bikes and those were Premix... never had this issue when tuning say for larger carb and/or pod.

It seams to me in hindsight if you are going to run a larger carb, or PODs of your choice and you fear being too lean and start rich jetting. Not wise.... unless you premix too.

Again, I am surprised at the wear. Can't think why else this would have occurred: I suppose Too much gas washed the little oil from Injector pumping away from cyclinder walls.

Let me know if you agree

I am going to test my oil pump again to make sure nothing happened there (lines full no bubbles... NOS pump from P. Miller).

My cylinders are off the be rebored! $35 a hole (money tree blooming now it is Spring), Third time is a charm (#1 Failed oil pump, #2 failed crank (caused by #1), #3 can't leave well enough alone)
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Re: Too rich jetting can wash oil injection film away?

Post by Vintageman »

I was hopping for some experience on this,

Yes I got spanked for trying to mod my bike. How dare me do such a thing

Seriously.

I am about to put this thing back together, It just seams strange to me that an allegedly working oil injection even though the main was somewhat rich would cause the cylinder and rings to wear as if it has 30,000 miles for a 150 miles of riding. Piston did not looked like it was worn (no Score lines for example), but did not measure and will.


I think if I had no oil at all and when not WOT to expose the main too rich the skirt would show intake signs scoring?

I think I will run 50:1 mix for a bit a long with injection just in case.

Just never seen this kind a wear. AM I missing something
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Re: Too rich jetting can wash oil injection film away?

Post by Vintageman »

It did it again!%#&!

Can't be too much fuel … All stock now.

Within ~100 miles the rings were shaved thin. Some sides more than others, but no groves just worn smoothly thin all four rings. The cylinder areas were the ring travels about suffers too . There is a ridge on top for example and more wear about the transfers.

Comparably the piston looks better and shows minimum wear. The lower half of cylinder has fine lines which I attribute to piece metal getting picked up. See this in piston too but don’t feel like you do in cylinder wall with finger nail

Fresh bore and I started with 2 gal in tank 64:1 in the oil tank, but would foul plugs as I opened it up some. Came back after 25 easy miles and poured no mix gas to fill tank. I think after this it wore faster not sure though. 100 miles is not long time

It has a new oil pump I bought of P. Miller and when installed (before this post) The lines are full of oil now, no air and I could see oil in the areas, under piston, when I pulled top end off. Never really saw smoke coming out of my pipes.

:?: What the heck is the problem that causes the rings to wear so fast so much.

:?: Has any experienced this before

It must be lack of oil I am thinking pump no good.

Suppose I could test pump again with cover off and drill.

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Re: Too rich jetting can wash oil injection film away?

Post by Craig380 »

Sorry to hear about these woes with the 250.

The only thing I can think is this: Is the oil actually going into the cylinders from the oil jets?

I don't know the exact set-up on the 250 twins, but on the aircooled triples there is a brass oil jet in the inlet stub on each cylinder, which is fed by a drilling in the crankcase, which leads to the oil line banjo bolt. There is a hole in the paper base gasket to allow the oil to pass from where the oil line attaches, up to the oil jet.

Are the oil jets clear? Is there a hole in the base gaskets to allow the oil to pass?

I can't think of any other reasons right now ...
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Re: Too rich jetting can wash oil injection film away?

Post by jabcb »

Did it happen pretty much to both cylinders or was one cylinder much worse than the other?
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Re: Too rich jetting can wash oil injection film away?

Post by Suzukidave »

I dont know about the 250 but with the 750's its possible to mount the control arm on the pump 180 deg out so at idle its full oil and at full throttle there almost no oil ? If the 250 pump is anything like the 750 as the pump control arm moves to full throttle the pump drive on the bottom moves up into the pump .
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Re: Too rich jetting can wash oil injection film away?

Post by Vintageman »

Craig380,
Yes, good questions, base gasket holes do line up with injector feed holes and have a brass pipe and all clear.

jabcb,
Both cylinders pretty much even

Suzukidave,
180 degrees out. That is interesting.
The GT250 is just like the T500 overall. Can the T500 be set 180 degrees out?

I did note the arm was different (longer or shorter ) when I bought it from P. Miller and I swapped arms.

By 180 do you mean I could have rotated the shaft 180 degrees when I put the arm on? The Arm is set at 12 O’clock Idle and turns clockwise. I need to check this 180.

I suppose I should take clutch cover off and run the oil pump shaft with a drill and watch it pulse oil out.
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Re: Too rich jetting can wash oil injection film away?

Post by Alan H »

Never heard of anything like this - ever.
Could be either lack of lubrication to bores, poor quality/incorrect profile rings or perhaps bores not honed correctly?
The amount of oil in the bores is minimal so I can't see that being an issue if there is enough oil getting to the bearings.
The throwers next to the bearings should direct drops of oil from the bearings to the underside of the pistons/bores. How smoky were the exhausts when running?
What oil are you using?
How much oil was used from the tank in 150 miles of running?
Just a thought regards the rings - they fit the piston grooves with no movement vertically in the grooves?
Some rings are chamfered on one side so they can be fitted incorrectly (upside down) - this normally would mean that the rings wouldn't go all the way into the grooves though so the pistons wouldn't go into the bores 'nicely' but would be very tight if they went in at all. It is possible to fit chamfered rings into parallel shaped piston grooves though, and the rings would 'chatter' and wear quickly.

Grasping at straws here. :wth:
Think of how stupid the average person is, then realise that half of them are more stupid than that.
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Re: Too rich jetting can wash oil injection film away?

Post by Suzukidave »

Vintageman wrote: Suzukidave,
I did note the arm was different (longer or shorter ) when I bought it from P. Miller and I swapped arms.
By 180 do you mean I could have rotated the shaft 180 degrees when I put the arm on? .
Yeah .. thats what can happen at least with the 750's , the shaft coming out of the pump has flat sides to index the arm . But the shaft without the arm on it can be turned 180 deg and the arm with fit right back up just out 180 . Not saying this is it but its a thought a quick test to see if the arm is on correctly is to look at the drive shaft of the pump ( when its off the engine ) if its correct the shaft that drives the pump will move up into the pump as the arm is moved to full. Thats completely if they work like the 750 pump though .
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Re: Too rich jetting can wash oil injection film away?

Post by Vintageman »

The shaft has a flat side. Good idea, but should not be the issue

It wasn't until I changed the pump did the rings wear so fast. A new ring is
and around 0.080" the one that wore some areas were down to 0.065" Makes for a very large ring gap that thin. won't start easy. Top end gets real noisey and still was showing 125 pSI both side, Slow kick with hand I coul dtell it was loosing compression and since I been through this before I knew what happened.

It simply must be a lack of oil situation?

Or spirit of previous owner haunting the bike OOOOOOOOOOOOOOOOO

I am going to have to test the pump.
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Re: Too rich jetting can wash oil injection film away?

Post by Vintageman »

Alan H wrote:Never heard of anything like this - ever.
Could be either lack of lubrication to bores, poor quality/incorrect profile rings or perhaps bores not honed correctly?
The amount of oil in the bores is minimal so I can't see that being an issue if there is enough oil getting to the bearings.
The throwers next to the bearings should direct drops of oil from the bearings to the underside of the pistons/bores. How smoky were the exhausts when running?
What oil are you using?
How much oil was used from the tank in 150 miles of running?
Just a thought regards the rings - they fit the piston grooves with no movement vertically in the grooves?
Some rings are chamfered on one side so they can be fitted incorrectly (upside down) - this normally would mean that the rings wouldn't go all the way into the grooves though so the pistons wouldn't go into the bores 'nicely' but would be very tight if they went in at all. It is possible to fit chamfered rings into parallel shaped piston grooves though, and the rings would 'chatter' and wear quickly.
Just saw this now


I have never seen this before either.

Both times factory OEM pistons which came as a kit with rings

RPJ Performance did my boring as he has done some before on other bikes just fine. I did

The rings were gapped and placed writing side up. Also checked with calipers for the are Keystones

I never saw smoke out of pipes

I am running Motul 700, I use this and others full synthetic JASO FD in all my bikes

I never made it 150 miles. I took few rides maybe 20 miles, 30, miles and a couple under 10 miles.
Couple gallons of gas.

Thin ring fit grooves well. I did check gap were a 0.008' gauge fit through
I always wonder if they rings rotated about keying pin, But not eight times now. I don't think the piston would have fit if it did. My eyes are getting old but I use 2.5 times glasses a lot of light and make marks below key pins. Everything well oiled ahead and first start engine is nice and quite


Running the shaft with a drill (clutch cover off) you see periodic burts of oil, longer charges as arm is opened. I will empty line first to see them fill.

If the pump works OK I will be apprehensive and insecure to try again

It may be a few days before I try
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Re: Too rich jetting can wash oil injection film away?

Post by GT750Battleship »

:( Very rapid wear usually associated with straight petrol & little or no lubrication!!
I was speaking to a guy today whose nephew got hold of his Bultaco, & didn't realise it needed two stroke in the fuel!! He said he couldn't believe the wear to the bore,when he dismantled the motor!!! :cry:
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Re: Too rich jetting can wash oil injection film away?

Post by Suzukidave »

Did checking out the pump get you any answers ?
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