Specifications for 158

[pop]

you can buy a similar one from BIGW bicycle department for about 9 bucks

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I only have 20seconds to post then I get cut off

[Bully fanatic]

Hello Drew, I am not sure but I had a look on my 151 engine and couldn`t find anything so I would say you have to take the head off and measure the bore. A normal ruler is all you really need to measure the bore. I could be wrong though. Ross Brown would know for sure. cheers. Graham.

[brownie]

I think your right Graham the only way to be sure would be to measure it, my guess is and its only a guess is that all 158's would be 238 apart from some very early numbered 158's. In the parts book it only lists one part number for pistons and barrell they both start with 157 which is the Lobito T 238 prototype number, although the 4th oversize piston +1.00mm part number starts with 91 the previously used piston for a 250 from model 91. so you would use a standard 91 piston for your 4th oversize and and still have 4 to go.

[Bully fanatic]

Hello Ross. I am not sure either. I know the 158 I had in the very early eighties was a 72mm bore on second oversize (.50mm) and I can remember it still seemed to have plenty of meat left in the liner. Unfortunately I can`t remember what the engine number was on it. A mate has one now but I don`t think he would be to keen on me just stripping it down to have a look even though I could probably do it in an hour. Maybe it needs a decoke by now anyway. I actually had the head on it all loose a while ago so I could lend the head stay to another mate ( Bogwheel ) so he could get one made. I didn`t pull the head off it though. I know that trying to buy rings was always a pain until I measured the bore and asked for that size rings. Graham.

[brownie]

Yeah Graham go and whip that head off and see what number is stamped in the top of the barrell, it would definitely need a decoke by now, a lot more fun than watching some stupid cooking show on the TV

[BOGWHEEL]

Have been curious myself, but keep forgetting to measure the thing. Mine (M158--380 on std bore) is in bits at present.
I will measure it tonight (if i remember)

[BOGWHEEL]

Sorry - forgot again.
Tonight for sure

[sherpa]

Hi my understanding is that all 250 sherpas from 158 onwards were 238 [71mm bore]. The reason this was done was to avoid higher rego costs which escalated greatly for 250's.The very first batches of 158's had the 238 sticker, later batches were changed to a 250 sticker but still had the 71mm bore, apparently buyer resentment at the 238 tag caused the change. My 158 manual has on the cover photo a bike with the 250 sticker as are all the photos in the book. Of more interest to me is the different frame the 250 had in comparison to the 325- different forks, bottom triple clamp is shorter, different airbox, shorter wheelbase, more ground clearance- does anyone know why? From 198/199 on the frames are the same for both engines
Cheers Greg

[Justdrew]

Thanks everyone for the input. I had the bike running really well two weeks ago, the lights even worked. Since then I've been giving it a bit of TLC and now the thing won't start!! I'm going to put a new set of points and condensor in it and hope to fire it up again soon. I have spark but not a really big bright blue one, plenty of compression and fuel. I really dislike MK2 Amals, compared to the old tickler on the Metralla.