Motorcycle General Discussion

[David Clark 13Participant @davidclark13]

As well as for Model Engineer this forum is for Model Engineers Workshop readers, most who don't make models but do general engineering and restoration projects. The thread title says it all, you don't have to read it.

[WolfieParticipant @wolfie]

Motorcycles might be the subject for model engineers of the future!

Have added a heading for Motorcycle restoration so any bike talk can go in there

[John Stevenson 1Participant @johnstevenson1]

Posted by Wolfie on 30/10/2015 19:14:26:

Motorcycles might be the subject for model engineers of the future!

Have added a heading for Motorcycle restoration so any bike talk can go in there

.

Hang on.

You have started a fresh thread in the fresh thread that was stared for motorcycle topics

[John OlsenParticipant @johnolsen79199]

On the centrifugal force thing…centrifugal force only exists if you use a rotating frame of reference. So if you are in or on a vehicle, and it makes a turn, it will appear to you that there is a force acting on you and the vehicle outwards from the centre of the turn. However, to a fixed observer there is no such force and what they see is that the vehicle is tending to go in a straight line, as Newton said it should, but a force from the tyres, wings, or whatever, is forcing it to follow a curved path. It follows that if that force is removed, by the wheels hitting a slippery spot or the wings falling off or whatever else, the vehicle will continue in a straight line.

We don't usually use rotating frames of reference for anything much since they make for complex dynamics. For instance fixed objects at large distances will appear to be orbiting around your centre of reference at really high speeds.

On the countersteering thing…that is really the only way that steering on a two wheeler works. If you look at the tracks of a bicycle in soft ground you can see that the two tyre marks cross from side to side over each other as the rider steers to keep the centre of support under the centre of gravity. This is similar to the process of balancing a broom handle on the palm of your hand, except the bike is only free to fall over in one plane. At low speeds the movements of the handlebars are quite exaggerated, at high speeds they are minimal, amounting to just a little pressure on the inside bar as you set up a turn.

Ignore anyone who tells you the gyroscopic forces are involved, they are negligible, and bikes have been built with counter rotating flywheels to cancel any gyroscopic forces from each wheel. Riding such a bike is no different from riding a normal one.

John

[Phil PParticipant @philp]

Here's my two, the 1972 XL250 Honda was restored about thre years ago and gets used every day for work in the Summer.

The 1950 BSA 350 B32 with Goldie engine bits only comes out when it is guaranteed not to rain.

I restored this one in 1983.

I have had over 70 motorcycles of various types over the years, but just have these two and the 1936 Austin Seven Sports car now.

Phil

[HopperParticipant @hopper]

On the modelling side, how's this for a project:

[LathejackParticipant @lathejack]

Phil P.

Your Honda XL250 is a gem. The Japanese made some great looking trail bikes throughout the 1970's, far better than the later exaggerated, almost abstract styling that began to appear in the late 80's.

[Nick_GParticipant @nick_g]

Posted by Raymond Anderson on 30/10/2015 18:28:11:

A put put forum might be a better place for this.

.

Hold on.!!!!!!

Why are you now talking about 1950's motorboats.?

Nick

[LathejackParticipant @lathejack]

I mustn't let er indoors see this pic, but a few months ago when I bought this 1969 BSA after almost 25 years since I packed them in I couldn't resist bringing it indoors for an hour or two.

As I went about my business I would just stop and gaze at it, a little in shock and amazement at my sudden return to bikes after all those years. Despite the old bit of carpet underneath, it did not leak a drop of oil.…………..A couple of weeks ago I also bought this complete spare BSA 250 engine, from you know where. I am just starting to dismantle it to reveal all the horrors that lurk inside. This is one of BSA's last four stroke single engines from 1972.

[John OlsenParticipant @johnolsen79199]

Lathejack…if that engine is the same as the one that was in my 1971 Triumph Blazer SS (badge engineering!) then there are a few things to look out for. The exhaust valve guide in mine was aluminium bronze. If you read Phil Irvings books, you will find that aluminium bronze is not considered suitable for exhaust valve guides. Mine had about 1800 miles on the clock when I got it, and the guide was loose in the head. I replaced it with cast iron, which was still in there when I sold the bike with over 25000 miles on it.

Also, there are two sets of timing marks. If I recall correctly (about 40 years later) one gear has a dash, and the other has a dash and a V. Contrary to what you might think, you don't line up the two dashes, you line up the dash and the V. The guy before me had done it the way that seems obvious, and then had not been game to run it because of the loud tapping noise. This was the exhaust valve touching the piston….I found the documentation about the correct setting, fixed it up, then bought it from him. The reason he had been working on it was that a cam follower had broken. The earlier ones apparently did not have enough radius where the round part meets the flat head part of the follower.

Of course the Amal carb has the usual habit of deciding to leak petrol out all over your right boot. This can be a little disconcerting. I don't advise running without an aircleaner since if it leaks out petrol like this and then backfires things would get very exciting.

Later on I had a gudgeon pin break, but only on one side between the piston and rod, the other side did not let go, although it had a crack lengthwise. I fitted a bush since the little end was scored, and replaced the piston and rings while I was about it.

The clutch needed lots of attention. Main problem was the slots in the hub wearing into a ripple pattern, which made it grab and hard to pull in. The quick solution is to file them straight but now there is more play and they wear again. Eventually you need a new hub or maybe build up the slots again somehow.

So..something good about it…it had the 1971 frame with the oil inside, and the running gear was all the same as the bigger bikes. It was a delight to ride. The motor had plenty of power. My mate at the time had one of those XL250's as above…the Triumph 250 would absolutely eat it up, both on gravel roads and on tarmac, even though the Honda had an extra gear. But mine did spend a bit more time in the workshop! These motors had a high compression ratio and a fairly radical cam. I used to have fun telling two stroke owners to have a go at starting it.

John

[LathejackParticipant @lathejack]

John.

Yes, the engine is from a B25ss Goldstar. These engines have some improvements over those built up to 1970. The main ones are an extra clutch plate to reduce slippage, a cast iron oil pump that replaces the zinc alloy type and a beefed up conrod. I dont normally buy complete assembled engines, so I broke a personal rule buying this. I will post some pics of what I found.

Just a few days ago I did learn about the need to line up the V mark on the cam gear, Instead of the dash. The oil in frame 250 and 500 BSA singles seem to be two of the most elusive and mysterious bikes in the UK, certainly to me. In all my years I have never come across any of them in use on the road. I think a large number were built for export. So it is very interesting to here from someone who actually owned one.

It's also interesting to here how it compared to the Honda XL250 of the same period that Phil above has. But there is no doubt that the Honda engine is far superior. They have no real trouble from big ends, conrods, oil pumps or clutches , they tend not to break and don't wear out too quickly. The poor BSA 250 on the other hand can suffer a little more with those problems, but I still love em and wouldn't swap mine, I think!

Edited By Lathejack on 31/10/2015 02:32:37

[HopperParticipant @hopper]

Posted by John Olsen on 31/10/2015 01:15:50:

… my 1971 Triumph Blazer SS (badge engineering!) t…Mine had about 1800 miles on the clock when I got it, and the guide was loose in the head.

…The reason he had been working on it was that a cam follower had broken….

Of course the Amal carb has the usual habit of deciding to leak petrol out all over your right boot. …

Later on I had a gudgeon pin break, but only on one side between the piston and rod, the other side did not let go, although it had a crack lengthwise….

The clutch needed lots of attention. Main problem was the slots in the hub wearing into a ripple pattern, …

LOLZ, wasn't it the very next year, 1972, they closed the doors at BSA? (Barsteward Stopped Again!) I wish I had never sold this pair though. '56 Goldie, US spec. And '69 Rocket 3. Doh!

[Yngvar FParticipant @yngvarf]

It's just a hanger for band saw blades.

[CirclipParticipant @circlip]

Posted by Roger Williams 2 on 30/10/2015 17:29:41:

Did anyone see the Rossi – Marquez saga from Sepang on Sunday !!. I reckon Marquez was asking for it…..

Rossi finally gets a penalty. Anyone else would have had the race points docked but that would have gifted his team mate the world title. Bet Sete and Casey smiled at this one.

Regards Ian.

[OuBallieParticipant @ouballie]

Bike sounds:

My 350 emitted the most unusual exhaust note, unlike any other twin at the time I can think of.

Chap who lived up the road from us in Jhb, had a Trident and the first time my brother and I heard it we said "BRM" as it did sound like the F1 engine.

Geoff – Austin Seven duty today.

[Mike PooleParticipant @mikepoole82104]

I think we all countersteer subconsciously, once you are aware that this is how steering works it can be exaggerated to make a bike steer more quickly.

Mike

[JAParticipant @ja]

Posted by Michael Poole on 31/10/2015 11:24:30:

I think we all countersteer subconsciously, once you are aware that this is how steering works it can be exaggerated to make a bike steer more quickly.

Mike

Thinking about this further – something has to be done by the rider to disturb the bike from its straight path before they can go into a turn.

JA

[GarryCParticipant @garryc]

Posted by Roger Williams 2 on 30/10/2015 17:29:41:

Did anyone see the Rossi – Marquez saga from Sepang on Sunday !!. I reckon Marquez was asking for it…..

Agreed Roger, Marquez was given exactly what he was asking for – brilliant defensive riding by Rossi (as usual)..

[Nick_GParticipant @nick_g]

Posted by Michael Poole on 31/10/2015 11:24:30:

I think we all countersteer subconsciously, once you are aware that this is how steering works it can be exaggerated to make a bike steer more quickly.

Mike

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I agree.

It's only when I became aware and started thinking about counter steering that I realised I was already doing it.

Nick

[WolfieParticipant @wolfie]

Haha Oh dear never noticed that

Posted by John Stevenson on 30/10/2015 20:27:19:

Posted by Wolfie on 30/10/2015 19:14:26:

Motorcycles might be the subject for model engineers of the future!

Have added a heading for Motorcycle restoration so any bike talk can go in there

.

Hang on.

You have started a fresh thread in the fresh thread that was stared for motorcycle topics

[WolfieParticipant @wolfie]

When I'm not fixing a BSA….

[GarryCParticipant @garryc]

Hi Wolfie

I used to have a baby one, not many places in Wales I didn't get to on it…

Cheers

Garry

[Ian AbbottParticipant @ianabbott31222]

Finally peripheral neuropathy forced me to quit riding. When I stopped and put and foot a down my ankle gave way. It became too embarrassing when bystanders had to keep lifting the bike off me.

The wife was upset when I sold the Royal Enfield, she loved being the tottie on the back……..

I keep thinking that I should try for something with training wheels.

Ian

[Roger Williams 2Participant @rogerwilliams2]

Here's me rotary…

[John OlsenParticipant @johnolsen79199]

Lathejack..the 1971 Triumphs and BSA were pretty rare in these parts too. Mine was the only Blazer SS that I ever saw or heard of on the road. (in a small country like this you tend to hear about things.) I did see one of the 1971 BSA street scrambler 250's (with the small front brake) years later and talked to the guy, but his had been brought in from the States. They weren't actually in production all that long as they were dropped when the factory went broke. I'm pretty sure that mine did have the cast iron oil pump.

One interesting thing.. I went to a bike show sometime in 1971 or so, and the BSA Triumph stand had the entire range of new models for that year on display. As well as the Gold Star labeled 250 and 500 single BSAs, the Triumph Blazer and so on, they had the Bandit and the Fury. For those who don't know them, these were the Triumph and BSA versions of a 350 twin that they were developing. Nice looking engine. They were never released and were dropped when they went broke. So what were the bikes I saw? Were they actual prototypes, or just mock up dummies with empty cases? Did they get shipped back to England or are they still out here somewhere? They looked complete and ready to go, but of course I never saw them run one. It is nice to imagine that maybe in a shed somewhere someone has these tucked away.

I do still wonder if the Blazer that I bought a few years later was the one that I saw at that show. There certainly never were many of them out here. It's good that you know about some of the weaknesses of that motor, I learnt about most of them the hard way. Actually, this is probably heresy, but the whole time I had that bike I was keeping my eye open for a suitable Japanese motor to transplant in. I would have liked one of the SL350 single engines from Honda, or maybe one of the Yamaha 500 four stroke singles, although the latter might have been a bit tall to fit in. The combination of the good handling from the British frame and running gear and the reliable Japanese engine would have been unbeatable. (Most Japanese bikes up to about that time were pretty mediocre around corners.) However that was a few years before the idea of motorcycle wreckers caught on here, and I never did see anything suitable. As it was, it certainly had its moments. There were times it would just decide not to start…then after maybe half an hour of messing around, checking spark etc, it would suddenly burst into life as if nothing had happened.

Although it was supposedly a street scrambler, with the high "breadbox" exhaust pipe, it was really more street than scrambler, and I put a Dunstall Decibel pipe on mine. It had the big front brake with the airscoop, same as the triples had that year. I know they found it a bit inadequate on the big bikes, but on a 250 it was just great. I do have some photos in an album somewhere. It was narrow enough that if you touched down the riders foot pegs in a corner, you were already sliding. I did that three times in the 25000 or so miles that I rode the bike. It had tapered roller bearings in the steering head, and needle rollers in the swingarm. A bike with a lot of potential, pity they hadn't developed a more up to date motor for it.

John

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