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Messages - scifi
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1
« on: July 22, 2026, 09:52:50 AM »
quote... is this a 250k? No it is marked as a CB250 G .. ( Superdream.?)
My list of hills to avoid now includes any with... Mud, Stones, Hairpins, or greater than 1:5 gradient.
2
« on: July 19, 2026, 09:38:11 PM »
I was at a Vintage Machinery Show near Corwen, and thought I would take my CB250 up the nearby Berwyn Mountain track.
All went OK for the first few miles, but as the road surface became more rocky I had to slow down to navigate a good line.
As soon as the revs dropped below 5000 rpm the bike just died and stalled out.
This is the sort of track that I have ridden on an old British 4 stroke single, and thought no more about it.
I now have a list of hills to avoid in the N Wales area, on this type of bike.... It's just got the wrong type of power.
3
« on: June 28, 2026, 01:24:09 PM »
Most piston aero engines specify a run-in period with mono grade low detergent oil. Maybe the same should apply to our bike engines..
Essential qualities and characteristics of a high-quality running-in oil include..
High Zinc (ZDDP) Content: Contains elevated levels of zinc anti-wear additives to protect highly stressed components like camshafts and lifters during initial startup and friction.
Low Detergent Levels: Deliberately formulated with fewer detergents and dispersants. This allows microscopic metal asperities to wear away smoothly, rather than suspending them or preventing the necessary friction to "bed in" the parts.
Zero Friction Modifiers: Avoids friction modifiers and molybdenum. Fully synthetic oils or highly slick lubricants prevent proper seating, which is why running-in oils are almost exclusively high-grade mineral oils.
Proper Viscosity: Typically a straight-grade mineral oil (such as SAE 30) selected by the engine builder to provide a specific shear rate that encourages proper seating while maintaining vital oil pressure.
4
« on: May 24, 2026, 11:03:10 AM »
Thanks everyone for your replies. I have just received a new seat lock from China ( £9 delivered.).
With the top removed from the air filter box, the 400-4 now goes faster than I will ever need.
5
« on: May 05, 2026, 11:14:01 AM »
Thanks Tricky Micky, my seat does not have those 4 rubbers, or anywhere to put them. So it looks as if I will have to run with the filter uncovered. Got a new seat lock on order, from China, should be here by end of the month. 
6
« on: May 04, 2026, 09:50:04 PM »
Well after looking at the air filter beneath the seat, I removed the air cleaner top lid and went for another test ride.
This time 70 came up after about 1/4 mile straight, with more to come.
I found that the air intake was masked by the seat, as the following photo may show..
The bit between the screwdrivers is the only bit not obscured by the seat....
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7
« on: May 04, 2026, 08:33:18 AM »
Thanks Tricky Mick for the seat info. I managed to undo the lock and open the seat. The air Filter looks brand new, so I will have to investigate further.
If the weather holds today I will try some further tests. I have compared the speedo with a Sat-Nav and they are within 2 mph of each other.
Mine is a Red bike, but I have several litres of JCB Yellow Paint, if all else fails. . . !
8
« on: May 03, 2026, 02:17:43 PM »
Thanks for the replies..
I'm putting two and two together here...
I am unable to get the seat to open, as the lock is stuck. Also the plugs are a bit sooty.
So maybe my air cleaners need cleaning, as it is most likely running too rich.
Thanks for all the replies so far..
9
« on: May 03, 2026, 09:56:39 AM »
Hi All, I am a bit underwelmed by my 400-four's top speed. I thought they were capable of 100mph laps of the TT, .
I have a local one and a half mile straight road, and find that it is difficult to get more than 65 mph from the 400 either in 5th or 6th gear.
Is this as much as they do, because of the Sit Up and Beg riding position..?
I Also don't like the six speed box.. Need to change 1st to 2nd, to 3rd, to 4th, just to get up to 30mph in the village. My old BSA could do all that in 2nd gear.
I am sure my old CB200 was quicker.... Any thoughts..
10
« on: December 09, 2025, 04:22:16 PM »
Thanks for all the replies. My CB250 has rubber manifolds without the access screw holes, so my gauges won't work on that machine. For the 400-4 I am following the O ring discussion, it is much like the main jet O ring on Mikuni carbs, that I have on my Yamaha ty175 ( think that needs 4.6 x 1.6 mm.)
btw, Our local Aero Club had an Altimeter Calibration Manometer, that could be used to test airplanes altimeters. We just needed to connect all the pipes together with Tee Pieces.
11
« on: December 08, 2025, 04:28:58 PM »
The only place in the UK for Ethanol Free is at airfields. My local garage only sells E10, and does not even have E5 these days.
Thank God the Budget kept our 40 year tax and MoT exemptions. I would hate to pay for all that on my fleet of vintage bikes.
12
« on: December 08, 2025, 04:04:48 PM »
Hi All, I have several Hondas, including a cb400-4 that runs really well. I recently bought a 4 gauge meter for it and can see that the inlet manifolds have removable screws to connect the pipes. What should I adjust (at tickover..?) It probably need no adjustment, but I just want the practice. The only problem I see, is that the number 8 plugs ran sooty, but when I used number 7 plugs, the central electrode was a perfect colour, after a 2 x 30 mile run. The sootyness must be a high revs jetting, but the 4 gauges won't find this out, will it..?
My CB250 however sometime fails to start on two cylinders, and is more in need of synchronising, but I can't find any removable screws on the manifolds.
Any tips for anyone that has used these gauges, will be warmly welcomed.
13
« on: October 22, 2025, 08:41:50 PM »
Most four strokes have a position where at TDC the valves are 'Rocking'. So if you get your multi cylindered engine to TDC, one set of valves will be rocking.
For real accuracy, you could measure the piston movement with a Dial Test Indicator ( DTI.)
There may be some very rare exceptions to this rule, where there is some designed asymmetry of the camshafts.
14
« on: September 21, 2025, 12:24:42 PM »
It could be from a CB250, with the yellow segment starting at 9200 rpm.
My CB360T has a red segment starting at 9500 rpm.
and my CB500-foue is white starting at 10,000r pm.
All the segments stop at 11k and all the drives are slanted.
15
« on: September 18, 2025, 12:24:29 PM »
I used to ride around town on a Raleigh Winged Wheel (25cc.) with R in the fuel...
btw.. I think the modern Speedway oil is Millar's CB40 Caster oil.
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