frank bagley Posted October 10, 2012 Report Share Posted October 10, 2012 Can anyone help with an issue relating to B40 / B44 engine specifications? I have bought a B40 to convert for Trials. The B40 Engine has a B44 round Aluminium barrel with std bore. Found so far;- B44 Al. round Barrel marked 41-42 with a gasket face to face of 82.4mm B44 piston 41-571 (std bore) B44 con. rod marked 41-550 Problem When turning the Engine without the Head the piston at TDC is above the Barrel by approx. 3mm Same problem with a std B40 piston 41-075. I believe the Barrel has been reduced in length but suspect machined too far. really would like to use this Aluminium Barrel, The B44 con rod results in a stroke of 90mm (not 70mm as B40). Questions;- - What is the B44 Round Alunium Barrel length gasket to gasket face? - If I have interpreted the issue correctly then one option would be to add a spacer between the barrel & crank case to correct back to the B44 barrel length enabling me to use the B44 push rods. Can anyone suggest a supplier for the spacer? - I want to achieve a compression ratio of 6 or 7:1. By returning to the B44 barrel length, what ratio would I achieve with the B40 piston? - Are there alternative 79mm dia. pistons to achieve the desired compression ratio. I hope there is someone out there much smarter than me to help me out. Any help is much appreciated Frank Mobile - 07989 566 219 Quote Link to comment Share on other sites More sharing options...
cvgmmartin Posted October 10, 2012 Report Share Posted October 10, 2012 The conrod length has no effect on stroke only the crankshaft sets the stroke, and if you are currently measuring a stroke of 90mm then you don't have a B40 crank. A 79mm bore with 90mm stroke gives a 441 cc engine. Quote Link to comment Share on other sites More sharing options...
frank bagley Posted October 10, 2012 Author Report Share Posted October 10, 2012 Hi Cygmmartin Good point, just measured 70mm stroke ie, B40. Would still like to understand B40 & B44 Barrel lengths from gasket face to gasket face? Anyone out there with a barrel on the bench please measure for me? This will allow me to modify the length of the B44 barrel using a spacer Thank's Frank Quote Link to comment Share on other sites More sharing options...
cvgmmartin Posted October 10, 2012 Report Share Posted October 10, 2012 There is a web site for Progressive Classic Products located in the West Midlands at Brierley Hill Phone 07713 106 278 or 01562 229 049, e-mail progclasprod@yahoo.com and they advertise spacers for BSA singles from 1mm to 15mm thick. I assume they still exist. Good Luck Quote Link to comment Share on other sites More sharing options...
frank bagley Posted October 10, 2012 Author Report Share Posted October 10, 2012 That's excellent - Thank's I have been in touch with this company a few months ago concerning footrest plates, give them a try tomorrow Thank's Frank Quote Link to comment Share on other sites More sharing options...
frank bagley Posted October 11, 2012 Author Report Share Posted October 11, 2012 I now understand that my B44 round Al. barrel has been shortened & to return to the B40 set up using the B44 barrel I need a spacer under the barrel Does anyone have the length of a B40 cast Iron barrel between mating faces (gasket face to face? This will allow me to decide the spacer thickness required Thank's Frank Quote Link to comment Share on other sites More sharing options...
cvgmmartin Posted October 11, 2012 Report Share Posted October 11, 2012 Contact Charlie Prescott through the The BSA Otter web site, he must have a barrel on his bench somewhere. Quote Link to comment Share on other sites More sharing options...
craig10 Posted October 11, 2012 Report Share Posted October 11, 2012 You'd be best working back from your wanted compression ratio with the piston you have before getting a spacer made, otherwise you might be out of pocket for another piston as well. Remember to check your valve to piston clearances using putty or similar when boxing it all up. You can find how to measure the combustion chamber volume, piston pop-up etc here http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=113079&page=2 , go to the 4th post by Dave_NV, then put your figures into this comp ratio calculator http://www.csgnetwork.com/compcalc.html . You can then just add increments to your head gasket dimension in the calculator to get what you will need. Hope that helps Craig 1 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.