ring end gap?

[sevenfifty]

Hi Guys, I had the cylinders off my 750 (long story about an unusual transmission problem – for another post) and I’ve got to replace the rings. The oil ring broke while going back together (#&#^@#*#(!!!!!).

The new set is on the way, but I can’t find the spec for the end gap in the workshop manual. What are the gaps for each ring? Thanks!

[jcslocum]

See here:

http://www.bevelheaven.com/manuals/750p ... es/071.htm

Make sure to push the piston ring down into the bore with the piston at least 1/2 way to make sure it's square.

[sevenfifty]

Thanks - yes it is right there in the manual. I don't know why I did not find it. What a dope. Thanks for the help.

[paso750]

how did you make those photos ? It looks like a miniature model

G.

[higgy]

Wide angle lense G
That is a very good shot,lots of depth

[silverfox]

If you can't afford the genuine rings, you can run Mitsubishi Eclipse or Dodge Neon (first over size=88mm).
These are 4 cylinder vehicles so you get 2 sets!!
I brought them in from the states for about US$60
Did have to get the pistons re-grooved a bit deeper but since I was getting them expanded already it was no big deal.
Have been running then 2 years now (15,000km) and my oil comsumption is the lowest I have had in 8 years.
Typical kiwi, where there is a will, there is a way

Nice photo's from Barber, nice to see a BRITTEN there from my home town, Christchurch, NZ.

Looking forward to a summers riding and trying out the new Michelin Pilot Road3 (160/60x17)

Tony

[sevenfifty]

how did you make those photos ? It looks like a miniature model

G.

Yep - 28MM wide angle lens on an Olympus SLR. I also have a 24x24 softbox light I was using. Light and depth of field give the effect. Photography is a hobby of mine. When I get on my personal PC, I'll post some more photos.

If you can't afford the genuine rings,

As for the rings, they are already on the way from Italy.

[sevenfifty]

I have to believe this has been discussed, but the Manual has a significant typo for the ring end gap for #3 (oil ring) in the US translation section.

The correct gaps for a 750 Paso are:

1st – 0.0118 – 0.0196 inches
2nd - 0.0118 – 0.0196 inches
3rd - 0.00984 – 0.0196 inches


The manual list the #3 oil ring as 0.0984, that is nearly a 10th of an inch, and quite improbable a dimension for a ring gap.

The metric listings are correct, and the 3rd ring calls for 0.025 mm or 0.00984 in.

Thought I’d point this out incase someone searches for ring gap, and finds this post in the future.

BTW, got it all back together, and motor hung back in the frame today. Plan to “smell smoke” and take her for a spin tomorrow.

[jcslocum]

great news, great catch!

Let us know how it runs.

[sevenfifty]

Well it was a long day, but I got the Paso running Sunday. No real problems, a few leaks had to be fixed, but it fired right up. Ran it up and down the street naked a few times and all the gears are there now. I’ll button it up this week, almost just in time to put it away for the winter. Some projects just take what they take in time.

The transmission problem was a strange one. Shifting up or down between fist and second could result in locking the transmission, and the rear wheel!!! Pulling in the clutch did nothing. The first time this happened I was turning into my neighborhood down shifting to first, so going very slow, and the back tire just locked up. I kept it up, but just.

After fiddling with the shift adjustments under the alternator cover, my bike buddy and I concluded there was a major malfunction, possibly a bent fork. So I pulled the engine, took off the jugs, and sent it to a guy in Long Island who has a few of these motors lying around (to steal parts from) and knows these transmissions with his eyes closed.

The root cause was a bit of flash in the case casting at the shift drum. So this was a factory defect. I should mention that this bike only has 10K miles on it. So we thought a transmission problem on this bike was very unusual right from the start.

The flash was enough to cause the shift drum to be shimmed wrong at the outset. Over time the flashing wore down or was beat over, and the shift drum had too much play, making 1- 2 shifts harder, and causing the fork to ride on the gear. This hard 1-2 shift then caused the rider (me and the last guy) to eventually bend the shift fork. The end result was this strange lock-up.

Replaced the shift fork, second gear (it was galled and had been eating into the fork). Clean up the casting, new shift drum shims from Italy and now it shifts correctly for the first time. Very strange problem to have with a Duc, and I'm glad to have it all back together now.

[Mc tool]

For those of you with 904cc engines subaru ( or thier after market suppliers ) do a 92mm ring set thay fits perfect and you get 2 sets for nz$80 instead of nz$600 for oneset of duke ones

[Duc906]

For those of you with 904cc engines subaru ( or thier after market suppliers ) do a 92mm ring set thay fits perfect and you get 2 sets for nz$80 instead of nz$600 for oneset of duke ones

You wouldn't happen to know the part number? What model Subaru they fit?

[Mc tool]

Sorry Ken I dont .Ionly found out immediatly after buying the duke ones . I was at an engine recon shop organising to have a set of rings made for an old vintage diesel engine i have ( 5 hp Blackstone ) and then asked the guy about making rings for the paso and the guy picked up a ring catalogue and found em straight away . I do recall that they were for a subaru DOHC 4 valve with nicasil ( or similar ) bores . Hope this helps