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Alan's B175 restoration
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Alan.Moore
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April 11, 2020 - 3:54 pm
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So the restoration of my 1970 B175 starts. The bike is all original and has had nothing changed since my Dad got her in 1979. Last on the road in the summer of 2004. My intention is just to clean her up and touch up a few rusty areas. 

After cleaning the carb and the points the old girl started up just fine. I thought there was a knocking from the engine last time I used her but to me she sounds just fine, but I'll know more when I can have a trip to the shops to get some supplies. There is a leak from the gearbox shaft so looks like some mechanical work will be needed.

There should be a video link below...hopefully

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1939 Ariel VH, 1942 Ariel WNG, 1951 Triumph 6T Thunderbird, 1970 BSA Bantam B175, 1980 Honda CB250N, 1986 Yamaha SRX600

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Blue Heeler
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April 11, 2020 - 4:36 pm
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Good progress, she sounds solid, ticks over very nicely.

Blue

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cocorico
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April 11, 2020 - 5:15 pm
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Alan.Moore said
...There is a leak from the gearbox shaft so looks like some mechanical work will be needed...

"They all do that, Sir"  wink Check the gearbox oil level first. There is no seal along the gear change shaft so any overfill with gear oil can easily find it's way along the shaft, especially with a bit of wear over the years.

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Blue Heeler
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April 11, 2020 - 10:05 pm
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Have a sniff of that g/box oil too, I had a few come into the workshop reeking of petrol and very diluted. Your bike starts and runs beautifully, so if there is petrol in your  g/box oil, it would`ve come from the proceeds of carb tickling seeping in through the top crankcase join where sealant has been known to fail.

I noticed your prop stand is on the left...some are on the right, so those are not good for leaking through gearchange-kickstart area.

My father had a piece of rag fitted to soak up leaks from this area on his Bantam, but I can`t remember exactly how he attached it...was nearly half a century ago. I do remember thinking it  was a bit Heath Robinson. He also continued riding for many thousands of miles with a broken gearchange spring!

I`ve not had any bad seepage on my Bantams. Maybe some have a blocked breather, if it`s not an overfill issue?

Blue

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Alan.Moore
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April 12, 2020 - 12:49 am
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Thanks for the comments. I will check the gearbox oil level.

Spoke to my Dad tonight and he said that when he last ran it in the eighties when it was under load it 'vibrated like mad'. I think I mentioned before that I seemed to remember some knocking and vibration when I ran it in 2004. So whilst it sounds just fine running on the stand I think I will have a look inside....I need something to do whilst we are still in lockdown. 

Checked the charging system earlier on...no real increase in battery voltage when revved. Checked the rectifier and the diodes all seem to be working OK. There is continuity through the alternator coils but I havn't checked the output yet. Just spent this evening redaing through mouintains ofposts on regulator rectifiers and charging systems...my head hurts.

 

Cheers

Alan

1939 Ariel VH, 1942 Ariel WNG, 1951 Triumph 6T Thunderbird, 1970 BSA Bantam B175, 1980 Honda CB250N, 1986 Yamaha SRX600

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slumanbantam
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April 12, 2020 - 7:24 am
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Ahh man I miss that sound.

1968 BSA Bantam D14/4

2018 Husqvarna Vitpilen 401

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cocorico
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April 12, 2020 - 7:51 am
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slumanbantam said
Ahh man I miss that sound.  

I know what you mean. I still feel like that when I hear an MZ going ring-ding-ding, or the burble of a flat twin Citroen.

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slumanbantam
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April 12, 2020 - 8:55 am
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cocorico said

I know what you mean. I still feel like that when I hear an MZ going ring-ding-ding, or the burble of a flat twin Citroen.  

MZ ETZ was my first ever bike!

1968 BSA Bantam D14/4

2018 Husqvarna Vitpilen 401

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cocorico
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April 12, 2020 - 9:44 am
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Alan.Moore said
...Checked the charging system earlier on...no real increase in battery voltage when revved. Checked the rectifier and the diodes all seem to be working OK. There is continuity through the alternator coils but I havn't checked the output yet. Just spent this evening redaing through mouintains ofposts on regulator rectifiers and charging systems...my head hurts...

If your battery is good you may not see much change. If you disconnect the alternator from the rectifier you should see the alternator output (ac) rise with revs. If you reconnect the rectifier and disconnect the battery from it, you should see the rectifier output (dc) rise with revs. The battery should be no less than it's rated volts across the terminals when the bike is not running and not a great deal more when running - if the voltage rises to 2.4V per cell, the battery is fully charges and any more will damage it . You probably know this with your restoration experience anyway! Reg / Recs are a perennial question, if you think you need one I'd suggest a 12V conversion (see FAQs), if only from the point of view that 12V regulators seem to be more abundant and reliable than 6V ones.

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BASIL
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April 12, 2020 - 9:56 am
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Hi, just before you start striping it down to find the knock take the air filter pipe of the carb start it up and when you hear the knock put you finger in to the intake of the carb and gently push it on to the throttle slide if it stops "knocking" you have found your problem a worn carb, I had the same with a B175. Regards Basil.

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Blue Heeler
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April 12, 2020 - 10:52 am
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Once had an alternator rotor nut work loose on a D14 I`d recently bought....that caused knocking & vibration until I torqued it up. Quick one to check on & you can also see if there`s any play in that side main bearing while you have the cover off.                    Hopefully nobody`s fitted a D14 crank to your B175 engine. Don`t forget the ear to a long screwdriver trick for locating source of internal kerfuffles. Hover over the clutch etc...

Blue

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cocorico
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April 12, 2020 - 2:16 pm
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Blue Heeler said
...Don`t forget the ear to a long screwdriver trick for locating source of internal kerfuffles. Hover over the clutch etc...

I actually bought a mechanical stethoscope off Aliexpress a while back. It cost about 2/6d, post free and is very useful I find. - virus free, too.

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Blue Heeler
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April 12, 2020 - 3:51 pm
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cocorico said

Blue Heeler said
...Don`t forget the ear to a long screwdriver trick for locating source of internal kerfuffles. Hover over the clutch etc...

I actually bought a mechanical stethoscope off Aliexpress a while back. It cost about 2/6d, post free and is very useful I find. - virus free, too.  

I like it, must get one.

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Alan.Moore
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April 13, 2020 - 12:39 am
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Thanks for the replies...

My digital multimeter just goes ape **it when I try to measure any voltages with it so have had to us a 12v headlamp bulb (60/55W) to test. Alternator wires connected to the bulb  (yellow to one filament and orange the other) illuminate very brightly, but not enough to burn out the filaments, so its probably putting out a combined 100 watts or so ...anyway it appears to be OK.

Restored wiring and started on E (no battery).  (Rectifier diodes already checked and OK) So no battery...one filament of bulb connected to battery leads and the bulb was bright...so the rectifier appears to be passing voltage OK but clearly unregulated (because its not in the original system). I am used to dynamos with a voltage regulator so still trying to get my head round a system where the (rectified AC) voltage is not regulated other than by the load imposed by the ignition coil (and any lights) plus the battery. I can now see why a small sealed lead acid battery is NOT a good idea with this system. Even a 8AH LA battery would tend to overcharge if you rode long distances at high revs?

Is there any regulator/rectifier unit that keeps the E facility rather than the 12V type where you join the orange and yellow wires from the alternator together? 

Moving onto the carb. It has very little wear and none of the screws have been molested, its certainly not been altered since 1979. It is a 626/17 with RB stamped next to the number, the Amal site says B means it has the 'updated needle and needle jet'. It has a screw in pilot jet (25) and I can not see a brass pilot jet 'bush' behind the pilot air screw. The spray tube is the 2 stroke type. It has the longer needle jet holder and the jet (105) has the 4 stroke cross drilling (which ties up with the B updated needle jet reference?). The main jet is a 140. Looks like it should be a 180 so it looks like that needs changing. It floods, but the needle valve looks like the original white plastic job, as does the fuel supply banjo so I think a repair kit is in order.

Regarding the knocking/ vibration from what I can recall (it was 16 years ago when I last ran it !) it was very noticeable so definitely engine related so its going to get stripped and rebuilt.

I'll post updates as I get more into it.

Cheers

alan

1939 Ariel VH, 1942 Ariel WNG, 1951 Triumph 6T Thunderbird, 1970 BSA Bantam B175, 1980 Honda CB250N, 1986 Yamaha SRX600

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stubaker58
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April 13, 2020 - 7:50 am
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That’s a great project you’ve got, nice to see an original in such good condition.  

Regarding the carburettor ... I found, much to my surprise, that setting the float height correctly was the thing that had the most dramatic effect on the mixture.  Mine had been running rich, black plug and carbon all over the piston so I thought about reducing the jet size, even bought a small selection of jets.  Before changing the jets I lapped the carb flange and the bowl joint surface and then reset the float height.  I now have a perfect chocolate brown plug (and several unused main jets!)

Maybe someone reduced your main jet to weaken the mixture but in fact the float was too high like mine?

Just a thought.

Regards.

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

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cocorico
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April 13, 2020 - 8:25 am
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DMMs do not like measuring AC volts on spark ignition engines - you could try using longer test leads to put some distance between the meter and engine, but an analogue meter would be better. As you say, rectified AC still varies with revs. You can get 6V regulators, but as you can see from the discussion, it's a vexed question. Read closely and you may find some recommended ones, I think Mike pbx posted one, or Peter G - the main problem is finding one with a good enough power capacity. Can't help with the carbs.

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Alan.Moore
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April 14, 2020 - 10:43 pm
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Stripdown

So today I set about the disassembly. Interesting assortment of spanner sizes needed, some nuts and bolts appeared to be AF sizes, others BSW. It all came apart pretty easily. Hardly any of the bolts etc were rounded off so I don't think it has been apart many times, if at all. 

SDC13351a.jpg

Engine has clearly been apart before, but again nothing really chewed up. Rotor and gearbox sprocket came undone easily with the air impact gun.

Piston is +20, looks almost brand new. No varnish at all on the underside and I can still clearly see the machining marks under the light scores on the thrust faces. I don't think it has done many miles. Its at AE 17952 and casting marks inside suggest it was cast in 1977. Bore is fine, no marks and no lip at all.

SDC13368b.jpg

Onto the conrod/bigend. I have read through loads of posts and it seems that the 'grinding' marks on both sides of the rod are 'normal' or at least not unusual. They extend well past the height of the flywheels at the top and are clearly very fine intentional 'grinding marks' the sort you get with a fine wheel on a bench grinder. (On the left side an E has been engraved in the rod, presumably to show which way round it was meant to go back in?).

SDC13368c.jpg

 

SDC13369c.jpg

 

There is no up or down movement at all on the big end (which rotates very smoothly) and 35 thou total sideways when slid along the crankpin. The conrod does not touch the flywheels when it is slid sideways on the pin. It does touch if you tilt the conrod sideways but there is no evidence that the rod has been contacting the flywheels....does this all sound as though the big end is Ok ?

I am splitting the cases tomorrow so will update with what i find.

Cheers

Alan

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April 14, 2020 - 11:30 pm
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Alan, I`d be well-chuffed if my D14 engine was as good as your B175`s ....can`t fault it thus far 🙂

Hope you find the vibration culprit when you split the cases. Maybe a faulty main bearing?

Did you fabricate your bike bench, looks like a fine example?

Blue

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Alan.Moore
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April 14, 2020 - 11:37 pm
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I hope I can find something. I have noticed that I have no end float on the crankshaft so something amiss there.

Yes I built the bench myself from 4 x 2 with a 20 mm plywood top. Its on wheels for moving about with small screw down feet to level it when in position. Probably a bit over the top, but after restoring my triumph 6T on a wooden box I decided I needed something a bit sturdier. There is a six foot long detachable ramp to get the bikes up.

Cheers

Alan

1939 Ariel VH, 1942 Ariel WNG, 1951 Triumph 6T Thunderbird, 1970 BSA Bantam B175, 1980 Honda CB250N, 1986 Yamaha SRX600

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Alan.Moore
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April 16, 2020 - 9:59 pm
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The cases are split, crank and bearings out. Hopping I was going to find something to explain the knocking...nothing yet.

Before I split the cases I did notice some gearbox oil on the flywheels and had noticed it smoked pretty well when first starting it up. What I found was gearbox oil in the crankcase...well the gearbox was fully drained before the cases were split so either it was leaking in through one of the seals or the joint between the cases. You can see some in also in the voids of the crankcase. There was hardly any gasket cement on the joint faces, but what was there was still soft!. Its red Hermatite and the engine has definitely not been apart since 1979. Its usually as hard as a rock after all that time.

 

SDC13381a.jpg

SDC13383a.jpg

Regarding my lack of crank end-float there were two 3 thou shims in, one each side. I removed them and refitted the crank...8 thou end float so it had been running with just 2 thou. The bearings were a bit of a mixture...a Hoffman, an EBC and an SKF, no markings to say they are C3 clearance. Cleaned out and all run smoothly with no excessive play. The crank is a nice sliding fit in the bearings.

The generator side oil seal had one flattened area of wear on about 1/3rd of the the lip, where it runs on the mainshaft. No sure but this may have been allowing some of the gearbox oil in. Anyone any idea why the wear is just in one place?

Clutch and gearbox look fine, no chipped teeth and little wear on the the clutch basket or plates.

SDC13378a.jpg

Checked the big end again....cannot feel any play up and down but as I said earlier there is side to side along the pin and at bottom of the stroke it is possible for the rod to touch the flywheel on one side. There are very slight marks on the rod at this point.

SDC13397a.jpg 

I don't think the rod touching the flywheel would account for the vibration from the engine...what do others think?

Also...why are the rods ground like this, the only thing I can think of is to prevent contact with the flywheels so is this something which was done at the factory ?

Otherwise I am at a loss as to why it vibrates.

Cheers

Alan

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