New 250 Project Adventure

[Snakeoil]

No excess wear. The damage observed to the pump was dirt, plain and simple.

Rob

[BDang]

Dirt on the drive gear side but not on the driven gear?

Regards,
Brian

[Snakeoil]

BD, your very logical question made me go out and pull the oil pump apart again.

There is some scoring on the driven gear side of the housing as well, but not to the degree that the drive gear side is scored. Looking at the drive gear/shaft/housing relationship with a much more critical eye indicates that you are correct. There is some slop between the shaft and the bushing that allows the drive gear to rub the housing. I can get a 0.003" thick piece of paper between the gear and the housing on the drive side, but it will not enter on the driven side.

Unfortunately, I only have dial calipers here at camp and they are not good enough measure the ID on the bushing and compare it to the shaft OD. I did find that the shaft is 0.002" out of round at the very top where the drive blade is machined.

But I also think dirt played a role here because the tips of the gearteeth are relatively smooth and do not mirror the scoring on the housing. I suspect that in addition to the gear possibly rubbing the housing, larger pieces of grid could pass over the gear tooth tips (apex) and make larger score marks. The score marks on the driven side are much smaller which would correspond with the tigther gear to housing clearance.

So, the question is, does the bushing need replacement or will it be serviceable in this condition? Replacement is a pretty simple process. And I can always machine a new bushing if they are not readily available. So, I guess I'll be making a small mandrel and pushing out that worn bushing.

Thanks for pushing back on my somewhat pig-headed opinion that it was simply a matter of dirt.

regards,
Rob

[BDang]

"the question is, does the bushing need replacement or will it be serviceable in this condition?"

Hi Rob,

with too much radial plays between bushing/shaft, 2 issues:
a) drive gear touches and gouges the soft AL housing
b) air could be sucked in through the shaft/bushing gap leading to low efficient (low pressure) pump. This might be the killer here

Regards,
Brian

[BDang]

Looking at this steel face plate and the scoring pattern of the drive gear (top circular area), the concentric deep score circles are more profound from 4 o'clock to 7 o'clock, and less for above area. This shows the drive shaft was pushed outward (or upward in the photo) causing the drive gear face no longer parallel to the face plate (top out and bottom in) and only the bottom of the gears were scoring the plate. Another way of saying too much plays at bushing/shaft.

Regards,
Brian

[Snakeoil]

Yeah, I plan to address this. Not sure if that bushing is available. But easy enough to machine one if not.

Have not touched the bike since pulling the pump out again. Headed out to my friend's storage area to get the remainder of the bits needed to build a complete motor/bike. I'm hoping he has a an assembled motor out there. Matched bevel drives being one reason. Maybe he's got one with a bad bottom end. That would be perfect.

regards,
Rob

[Snakeoil]

Went out to my friends container, which is a 43 foot tractor trailer box. Got another engine that he found in a dump. I've already started to strip it and the top end internals (cam, rockers, etc.) is all good and so is the bevel drive parts. Bottom case was broken and at first glance thought it was catastrophic failure. But I was able to get the crank to rotate and get the cylinder spigot out of the case. Piston is stuck hard. Closer examination indicates that the piston was probaby stuck and someone tried to split the cases by hitting them with a hammer. Destroyed the left crankcase. I hit a standstill since I have no pullers at the lake. So will pack it up and take it home.

Did pull the oil pump apart. It was assembled to the engine without aligning the drive slot and it peeled to big burrs on each side of the pump shaft. Killed me because the pump was otherwise perfect. No scoring and still had oil in it. Might see if I can save the shaft. Had to file the burrs off to get it thru the bushing.

Got a nice tank. It's off a 350 and is very sexy. Few dents and rusty inside. But very fixable from first glance. Got another seat, but not sure it is for a 250.

Grabbed another head with valve train in it. No cam. But found another cam that looks good. Pair of later side covers/air filter. A 27mm Dellorto was all we could find. He had 4 or 5 to choose from. Grabbed some other misc stuff like footpegs, shift levers, sump plugs with level stick, headlight bucket, etc.. Headlight bucket had the wiring harness dangling from it with what appears to be a perfect headhight and horn switch. That was a nice find.

He offered me the rest of his Duc stuff for a decent price. There is one 350 that was pretty complete he said, but in parts. Quite a few cylinders with pistons. More heads. Misc bits and pieces. 3 or 4 250 bottom ends and I think 2 350 bottom ends. And I believe 1 250 frame and 2 350 frames. I'm thinking about buying it all. Although I hate adding crap to what I already have with us looking at moving South. More junk to move.

I'm wondering what those 27mm Dellortos are worth. I understand they were used on the Diana or GTs? Still learning about these machines. Gray hair hinders remembering the details.

regards,
Rob

[Snakeoil]

I've posted a few separate inquiries on various things I've come across in the process of getting the bits together to build and engine. It's about time I do a little updating here on this thread.

Photobucket has become a total PITA. I'm sure they have done this to encourage user to sign up for an enhanced, paid subscription. I may give it a try to get rid of the ads. My protection software is always stopping downloads from that site as soon as I log in.

I have 3 heads and over the past few days, stripped any components from them and today gave all three a good degreasing and a nice warm bath. The objective here is to pick the best head from the three for the engine build. Here's what I have. And I numbered the heads so I could keep track of the components that came out of them. I'll use those numbers here to help me keep them straight in my head.

Head #2
This is the head that came with the partial rolling chassis. At first I thought it might be a a 350 head. But upon checking the specs, it appears to be a Mach 1 or a Mark 3 head because the intake bore is 29mm. The other two heads measure 25mm intakes which aligns with the 24mm carbs in the specs. I also learned that 350 heads also have 24mm intakes.

This head has had port work done on the intake. There is also a compression release that has been nicely drilled into the tower side of the head. Actually looks like a factory installed release. What was left of the release was still in the head I can could make it functional again by making a few missing parts. The other differences with that specific head are the exhaust snout is shorter than the other two Monza heads and the fins, which look more like a row of lower teeth, and are just above the exhaust snout, are longer on that head. Lastly, it appears that the spark plug hole has been repaired with a steel insert that is very well done. Looks like it came that way from the factory.

Measuring the valve seats, the subject head has a 40mm intake and a 36mm exhaust.

Here is the head showing the compression release bore.


This pic is the same head, showing the combustion chamber and the intake bore which has been worked on. You can also see the other end of the compression release port opposite the SP hole.


This pic shows the subject head on the right and one of the other Monza heads on the left. You can see the longer teeth (fins) above the exhaust snout on the subject head. And I just noticed that the longer fins are angled in the opposite direction.


This pic is of the same two heads above. You can see how the exhaust snout on the subject head (left) is shorter than the Monza head snout on the right.

Here is the intake side of the subject head on the left with a 29mm intake bore and the same Monza head on the right with a 25mm instake bore.



The other two heads each have their own "issues". Both are what I believe to be standard Monza head with 24 mm intakes. Exhaust snouts are both identical and longer than the head above.

Both heads have the same valve sizes. Seats measure 37mm intake and 33mm exhaust.

Head #3
This next head that was on the engine my friend found in the dump. It still had the entire valve train inside. But the cam is worn so badly that there are ears on each end of one lobe. The other lobe has only one ear as it appears the rocker was not centered on the lobe. It has a few dings on the fins from being kicked around the dump. The head was pretty much the only salvagable part from the entire engine. Looking at the cam, I can see why it was in the dump. The spark plug hole on this head is in decent original shape. I had to cut and collapse the exhaust nut to remove it. It along with a torn off stub of exhaust header were still in the head.

Head #1
This head is in decent shape. But the spark plug hole has been enlarged to take a much larger diameter plug thread. The plug was still in the head and in spite of using heat and copious amounts of penetrating oil, the threads left behind are less than perfect.

Here is a pic of the head showing the humongous SP hole and the mating plug. The plug thread measures 18mm. Not sure there is an repair insert that could return this to a 14mm plug. Would probably have to machine one and my South Bend will not cut metric threads...Grrrrrrrrrrrrrrr.


So, if anyone is still reading by now, can you tell me if head #2 is indeed a Mark 3 or Mach 1 head? I realize that the intake port could have been enlarged on a standard Monza head. But those bigger teeth are different too.

UPDATE: I did a search here and found that the Monza valves are 33/37 as I measured and the Mk 3, Mach 1 heads are 36/40 as I measured. So, I guess my question is do I have a Mk 3 or a Mach 1 head?

I would also assume that with larger valves, I will need a hotter cam to take advantage of them. I'm leaning towards using Monza head for the high velocity and possibly better torque.

Thanks,
Rob

[Jon Pegler]

Head no.2 is Spanish, probably from a 350 Road.
The compression release would be a standard fitting.

Jon

[bikester250]

Regarding head #2, I'm thinking that the second hole was originally for a 10 mm spark plug.
My dual plugged Mach 1S has the second plug in that location. Also the valve sizes are the same as the ones in my head.
Phil