They could just be 67 year old originals. If the rings are the same then how is the compression?
Not for the squeamish....
- Thread starter Tom Walker
- Start date
By Happy coincidence the service manager at the company where I work ( that would be me) found a need for such an item this week, as an oil change is planned this weekend I will test it before risking customers equipment.
It came from Maplins £99.5, batteries or memery card not included.
Ah Thanks Eddy, that makes sense. Thats quite low CR ?
Presumably the petrol after the war was not too special.
What do most people replace them with if I do a re-bore at some stage?
Onw would have thought that for touring, between 7 and 8 would be perfectly ok, and give it a bit more pep.
Cheers, Tom.
Well TT, it would'nt be on 20 over from the factory would it?
Compression not good on rear cylinder, ok on front. I have been pouring Plus Gas in the rear plug hole on and of, with the bike jacked up at the back to level the piston, and rocking the engine back and forth, in case rings are stuck.
Then I will run it, and see what happens.
Tom,
Eddy isn't quite correct there.
E7/6 was nominally 6.8:1 but 6.45 with the compression plate under the barrel
E7/7 was 7.3:1
Time to buy the books!
Regards
Tatty
For what it's worth I have an Extech BR250 Video Borescope that records still jpegs or video at 640x480 NTSC. I also have all three 1 m cameras/probes made for this device, each having its own advantages. If anyone else wants to go down the hole with a borescope, the following optical characterization measurements I made on the probes will be useful information for them even if they buy a different one:
9 mm/0.35"-OD camera having a 45-deg. angle of view, which is approximately equivalent to that of a 40 mm lens on a full-frame 35 mm camera. Variable intensity LEDs are built into the end of this probe as well as the others, and the diameter of the 1 m probe is such that the diameter of the camera is what limits the size of the opening into which it can be inserted. Although the claimed focus distance is 1.5-2.5 cm /0.6-1" I find this probe produces useful images over a wider range than listed in the manufacturer's literature. Keeping in mind the further any camera is from the subject the lower the magnification of the image, I measured the following for the distance / magnification / resolution:
1 cm / 10x / 0.5 mm
2 cm / 5.2x / 0.3 mm
4 cm / 2.6x / 0.3mm
6 cm / 1.8x / 0.4 mm
8 cm / 1.3x / 0.5 mm
For example, if this probe is 4 cm from the subject the magnification of the image will be 2.6x and features as small as 0.3 mm will be resolved.
5.8 mm/0.22"-OD camera with 48-deg. angle of view (approx. equiv. to 44 mm). Nominal focus distance is 2-7 cm /0.8-2.8" but I found it useful at even shorter distances than claimed. The measured distance / magnification / resolution:
1 cm / 7x / 0.1 mm
2 cm / 4x / 0.1 mm
3 cm / 2.5x / 0.1 mm
4 cm / 1.8x / 0.1 mm
5 cm / 1.5x / 0.1 mm
Comparing this with the previous camera it can be seen that tradeoffs are made in order to have a smaller diameter probe. While this probe will fit into smaller spaces and give higher resolution, it does have to be closer to the subject for a given magnification and has a lower magnification for a given distance. However, if I only could have one camera/probe this is the one I would pick.
4.5mm/0.179”-OD camera with 63-deg. angle of view (approx. equiv. to 35 mm). Nominal focus distance is 2-5cm / 0.8-2”. I haven't characterized this one yet because I bought it more recently to inspect a particular region near the head gasket between the fins on a Gold Star. Even though its diameter is only ~1 mm smaller than the 5.8 mm probe, it was necessary in order to fit between the fins.
Anyway, even if you buy a different brand borescope the principles of optics are the same so built into its probe will be optical characteristics that may or may not make it ideal (or, possibly, useful) for whatever you have in mind. So, it pays to look into the specifications in detail before spending your money.
I suppose its all down to the budget. That looks like a better buy than the one we ve got. ours was £110 and I think the Extech is £200 plus, and probably a better bet.
Ah well we ve got it now!
Ah well we ve got it now!
In a sense, yes, but what it really comes down to is the specifications a unit has vs. the specifications you need. I've had this borescope for something like three years so it's possible another one with better specifications and lower price has come on the market since then.
This thread prompted me to characterize the smallest of the probes. For the 4.5mm/0.179”-OD camera:
distance / magnification / resolution
0.2 cm / 65x / 0.25 mm
0.5 cm / 24x / 0.13 mm
1 cm /13x / 0.06 mm
2 cm / 6.5x /0.13 mm
3 cm / 4.3x / 0.5 mm
5 cm / 2.6x /0.75 mm
As can be seen there's a fairly narrow range of focus to achieve the highest resolution but the magnification with this camera is well into the range of a binocular microscope (although, not quite with the same resolution as a microscope). For completeness, the size of the screen is 2x2.8" / 5.1x7.1 cm.
What the numbers don't show is the images start to get blurry below 1 cm although they still can be useful, and there is an obvious amount of fisheye distortion with this camera. Also, the illumination from the built-in LEDs in this 4.5 mm probe is marginal for distances much larger than 5 cm resulting in the auto-gain of the camera producing increasingly noisy images. All of which illustrates the point that there is more to buying a borescope than just hitting a buy-it-now button.
Like most specialized tools, a borescope is superfluous until you need it, and then it's indispensable. As a case in point, the only way to know if something sinister is lurking at the back of your UFM is if you look.