john b Posted August 20, 2016 Report Share Posted August 20, 2016 Just completed a bantam new build. Started with a 4 speed engine and heavyweight forks bought cheap off a lad at work. Frame kit from progressive classics, bantam hubs with new akront rims, everything else new or newly manufactured. Was it cheap ? Probably about £2500 without all of my dads labour or many "guvvys" from work but I think worth it and looks good. First try out tomorrow . Any opinions ? Cheers John 8 Quote Link to comment Share on other sites More sharing options...
john b Posted August 20, 2016 Author Report Share Posted August 20, 2016 Thanks Deryk ! Im no photographerso thanks for the advice ! Yes its for Chris as his pre65 ride hes doing really well on the twinshocks, this engine came up so decided to buikd a competitive bike for him whilst hopefully keeping it as true to pre 65 as posdible cheers John Quote Link to comment Share on other sites More sharing options...
old trials fanatic Posted August 20, 2016 Report Share Posted August 20, 2016 Looks good to me Just one question hope you dont mind. Why fit a Mikuni ? Just that it limits the places where you could use it. Not criticizing just wondering that's all. Nice bike though i hope you enjoy it. Mines STILL in the gestation stage run out of money and time Quote Link to comment Share on other sites More sharing options...
john b Posted August 20, 2016 Author Report Share Posted August 20, 2016 Hi there I just coudnt get it to run right with the amal so tried the mikuni. I had added a spacer between the barrel and carb so that may have made it run better anyway. Once Ive tried it,I may put the amal back on to see hoe it goes thanks for tne comments cheers John 2 Quote Link to comment Share on other sites More sharing options...
totalshell Posted August 20, 2016 Report Share Posted August 20, 2016 the magic of the bantam is that no two ever have the same jets/slide.. i really must say though that once dialled in they can be better than perfect.. worth the investment of the su carby and a complete set of jets.. i did and experimented for probably 9 months till it ran like a watch and power came like pouring cream.. 2 Quote Link to comment Share on other sites More sharing options...
hencam Posted August 21, 2016 Report Share Posted August 21, 2016 Thanks Deryk ! Im no photographerso thanks for the advice ! Yes its for Chris as his pre65 ride hes doing really well on the twinshocks, this engine came up so decided to buikd a competitive bike for him whilst hopefully keeping it as true to pre 65 as posdible cheers John Hi John, I like it, looks really nice, where did you get the alloy tail pipe/silencer from. I had same trouble getting mine to run nice, ended up with a new Amal in the end, despite none of the secondhand one that i overhauled looking that bad or worn. which ignition did you choose? Quote Link to comment Share on other sites More sharing options...
john b Posted August 21, 2016 Author Report Share Posted August 21, 2016 Hi there The silencer wad an ebay purchase. Not sure what it was off but was almost brand new. Volume of the silencer was the same as a friend of mines who I measured, so I has the inlet modified to take the bantam front pipe which i had angled to suit.Sounds nice and seems to run well. Cheers John Quote Link to comment Share on other sites More sharing options...
john b Posted August 21, 2016 Author Report Share Posted August 21, 2016 Oh, forgot it was electrex world ignition ! Quote Link to comment Share on other sites More sharing options...
aawil Posted August 24, 2016 Report Share Posted August 24, 2016 not often I like the trend for old modern trick bikes but I must admit I like your one I only have one question , I was taught that to get the ultimate carburation you should have a airbox of at least twice the volume of air that the motor needed before the filter as such all of the off road bikes that I have built over the years have been fitted this way with the largest air box I could fit in ,am I missing something or were the expert guys who taught me over 50 years ago wrong 1 Quote Link to comment Share on other sites More sharing options...
davetom Posted August 25, 2016 Report Share Posted August 25, 2016 @aawill , are you confusing the cylindrical foam filter with an air box, or have I missed something ?? Quote Link to comment Share on other sites More sharing options...
bashplate Posted August 25, 2016 Report Share Posted August 25, 2016 If you wanted an enclosed airbox, I see what your saying....but a foam filter with NO airbox has way more than twice the volume....or am I missing something? Quote Link to comment Share on other sites More sharing options...
john b Posted August 26, 2016 Author Report Share Posted August 26, 2016 Hi there I did contemplate an aluminium airbox with a beta style filter , but favours at work to make it are a little thin at the moment so maybe later. A lot of bantams I see have the foam filter so decided to go with that. It does sound like it sucks a lot of air when you open the throttle but runs ok. Originally I planned 40mm ducting to take the filter up under the seat (hence the cut out in side panel) but the ducting was just not strong enough. I've ordered a bultaco Sherpa filter today with a cranked inlet hose which should tuck it further in. Thanks for all comments ! And Deryk, I've told Chris he needs to keep an eye out ! Cheers John Quote Link to comment Share on other sites More sharing options...
aawil Posted August 28, 2016 Report Share Posted August 28, 2016 the theory is that to get instant throttle responce you need a lot of clean filtered air at least twice what the motor cosumes on a full throttle attack ,i cannot see how sucking air through a foam filter without can do the carburationany favours ,i have home made airboxes on both of my greeves outfits including one of the last factory bikes both run on std amal mk1 carbs with probably the cleanest caburation i have ever had, i 1 Quote Link to comment Share on other sites More sharing options...
floydbassman Posted August 30, 2016 Report Share Posted August 30, 2016 the theory is that to get instant throttle responce you need a lot of clean filtered air at least twice what the motor cosumes on a full throttle attack ,i cannot see how sucking air through a foam filter without can do the carburationany favours ,i have home made airboxes on both of my greeves outfits including one of the last factory bikes both run on std amal mk1 carbs with probably the cleanest caburation i have ever had, i Got any pictures of these airboxes? Reading this has given me ideas for my TFS. At present it has a Villiers air filter with a home made adapter to fit the amal concentric on the bike. Quote Link to comment Share on other sites More sharing options...
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