Search found 454 matches

by stew79
Sat Apr 06, 2019 8:28 pm
Forum: Tech
Topic: 1000-Series 2/4-stroke Concentrics
Replies: 85
Views: 5633
Flag: Great Britain

Re: 1000-Series 2/4-stroke Concentrics

this is all very interesting, but to use a steady air flow (or vacuum) will surely give a very different out come to a single cylinder engine ? a series of sharp pulses of vacuum, at a range of different frequencies, will move air at a different rate to petrol (or any liquid) being lifted up through...
by stew79
Wed Feb 27, 2019 7:02 pm
Forum: Project bikes
Topic: BSA B50T from Trial to Race bike
Replies: 25
Views: 2548
Flag: Great Britain

Re: BSA B50T from Trial to Race bike

hi claudio, the advertised advance / ret figures from electrexworld for the stk-010 have come up in several threads on here before. perhaps your one has a more suitable advance ?, but what is the timing at starting or tick over ? the best power i have seen proof of for a b50 is 53 bhp (only 500 cc o...
by stew79
Tue Feb 26, 2019 12:29 pm
Forum: Project bikes
Topic: BSA B50T from Trial to Race bike
Replies: 25
Views: 2548
Flag: Great Britain

Re: BSA B50T from Trial to Race bike

thought it was a graph from some one else,s bike ! (nearly 9000 rpm !) ignition retard at high speed will lead to overheating (not just the piston) do you no what your actual timing is ? as those electrexworld things are far from ideal
stew
by stew79
Tue Feb 26, 2019 10:32 am
Forum: Project bikes
Topic: BSA B50T from Trial to Race bike
Replies: 25
Views: 2548
Flag: Great Britain

Re: BSA B50T from Trial to Race bike

whats the max rpm ? the figures on the 2 graphs contradict each other. amazing power with the 2 stroke type ignition !
stew
by stew79
Mon Feb 25, 2019 10:13 pm
Forum: Project bikes
Topic: BSA B50T from Trial to Race bike
Replies: 25
Views: 2548
Flag: Great Britain

Re: BSA B50T from Trial to Race bike

hi claudio, thats a great bike with an excellent dyno figure at the end. (not many of them on here) i have many questions, why make your own carb ? and ignition ? squish clearance and % of bore ? comp ratio ? what fuel ? (must be ave-gas or better)
stew
by stew79
Wed Dec 19, 2018 10:01 am
Forum: Off topic
Topic: The science of engine combustion.
Replies: 15
Views: 2038
Flag: Great Britain

Re: The science of engine combustion.

skippy, 2 weeks ago i made some carb and regulator parts for a friends American engine which is very similar to this one (but half the size) its governor stops the points from opening, but is not linked to the carb. he runs his engines occasionally at shows but not with a proper load on them. this c...
by stew79
Tue Nov 06, 2018 9:45 am
Forum: Off topic
Topic: Star
Replies: 209
Views: 24596
Flag: Great Britain

Re: Star

12 volts 3.4 amps is 3.5 ohm
12 volts 1.7 amps is 7 ohms
temperature rise of coil (from 20 deg c) to achieve 1.7 amps will be to 291 deg c ????
more likely battery voltage after 10 mins is only 5.9 volts (or 10 watts)
after 30 mins (not just 10 mins) the spark will be even weaker, miss fire etc.
by stew79
Mon Oct 15, 2018 1:30 pm
Forum: News
Topic: B50 Speedway photos
Replies: 5
Views: 1427
Flag: Great Britain

Re: B50 Speedway photos

hi brad, have you seen on ebay an original electronic ignition unit, like the type that was used on the b50 speedway bike? still has the ft sticker on it.
stew
by stew79
Fri Sep 14, 2018 4:52 pm
Forum: Tech
Topic: Starting the Race bike! BSA B50
Replies: 29
Views: 3721
Flag: Great Britain

Re: Starting the Race bike! BSA B50

a question about the little button, i can see how it works on a small 2 stroke, but that cant generate much vacuum on the over run to open the valve at the wrong time. on a 4 stroke at say 5000 rpm, shut the throttle and it makes a lot of vacuum. wount that open the valve against the little spring ?...
by stew79
Fri Sep 14, 2018 9:24 am
Forum: Tech
Topic: Starting the Race bike! BSA B50
Replies: 29
Views: 3721
Flag: Great Britain

Re: Starting the Race bike! BSA B50

it all becomes clear, i didnt realize the std leaver is in an awkward place for the extra plug. but as the ex valve only has to be lifted 10 thou or so of its seat to release the compression, could a special tappet cover be made with a clever lever or arm to do that ? could be less work than loosing...
by stew79
Thu Sep 13, 2018 5:30 pm
Forum: Tech
Topic: Starting the Race bike! BSA B50
Replies: 29
Views: 3721
Flag: Great Britain

Re: Starting the Race bike! BSA B50

fit the std decompressor back ? in april was watching a man try to start a 500 single H*nda race bike on car driven rollers. he had removed the std decomp parts altogether ? they only weigh a few grams ? the thing was set up very badly so took dozens of attempts to finally run. must have taken half ...
by stew79
Wed Sep 12, 2018 10:13 am
Forum: Tech
Topic: Starting the Race bike! BSA B50
Replies: 29
Views: 3721
Flag: Great Britain

Re: Starting the Race bike! BSA B50

the compression may be a bit high, the 44mm carb may be way too big, but even with a more suitable sized one with the right jets, the timing is not going to help at all. looking at the info on the electrex web site, with 10 deg at 250 ish rpm as a start point, (which is a quite normal universally us...
by stew79
Mon Sep 10, 2018 1:33 pm
Forum: Tech
Topic: Starting the Race bike! BSA B50
Replies: 29
Views: 3721
Flag: Great Britain

Re: Starting the Race bike! BSA B50

36mm vm mikuni 270 main (1.42 mm dia) 35 pilot (modified mixing chamber size vm22 or vm13/352 is same) 159 p8 needle jet (2.7mm dia x 5mm tall spray tube) 6dh3 needle (middle position) 2.5mm air jet (or just a 2.5mm hole) no 3 slide (4mm cut away) will work with a 38 but 36 is easier to ride and liv...
by stew79
Mon Aug 06, 2018 4:17 pm
Forum: Tech
Topic: Crank Big End Nut tightening to 200 ft lbs
Replies: 11
Views: 1601
Flag: Great Britain

Re: Crank Big End Nut tightening to 200 ft lbs

hi denisj, 200 lbs is for a b50, is that what you have ? there are some treads on hear with some different ideas about the best way to do the job. or as its a bit specialize and needs to very right, just take it to a good engineering shop.
stew
by stew79
Wed May 09, 2018 4:13 pm
Forum: Tech
Topic: Fitting MX cam and 32mm carb - port match the head?
Replies: 5
Views: 1467
Flag: Great Britain

Re: Fitting MX cam and 32mm carb - port match the head?

hi ben, i wasnt going to comment on the step as i have never worked on a b50 head. (i dont think any ccm head had steps or non matching diameters though) but back in the day there was lots of folk law and stories around the inlet port on race tuned gold stars. some had steps or a smaller diameter he...
by stew79
Mon May 07, 2018 11:26 pm
Forum: Tech
Topic: Fitting MX cam and 32mm carb - port match the head?
Replies: 5
Views: 1467
Flag: Great Britain

Re: Fitting MX cam and 32mm carb - port match the head?

hi ben, the tm32 is basically a 2 stroke carb that will need lots of different jets to work on a 4 stroke. the tm33 pumper is a 4 stroke carb so it will probably come with base jetting that will work well. (probably with a bleed type needle jet)
stew
by stew79
Fri Apr 27, 2018 9:06 am
Forum: Off topic
Topic: Crankshaft experiment
Replies: 162
Views: 26712
Flag: Great Britain

Re: Crankshaft experiment

jack, i assumed the fuel was injected into the blower, not at the valves. i have often wondered about the small helix angle of the blower rotors, having an influence on local pressure, after all the type with the much greater angle are almost axial flow. the more i read and see the more i want to pl...
by stew79
Thu Apr 26, 2018 10:20 am
Forum: Off topic
Topic: Crankshaft experiment
Replies: 162
Views: 26712
Flag: Great Britain

Re: Crankshaft experiment

hi minety, as i see it there will be very little heat generated from the engine, and with so much fuel going through the blower with the air i doubt it goes over 50 deg c. i think methanol really is a wonder fuel and one day i will have a play myself.
stew
by stew79
Wed Apr 25, 2018 8:51 am
Forum: Off topic
Topic: Crankshaft experiment
Replies: 162
Views: 26712
Flag: Great Britain

Re: Crankshaft experiment

yes jack, i did read that (and all of this very interesting project) but i am trying to think of a way around the "out of ratio" problem that becomes worse the faster it runs. swash plate fuel pumps can have an adjustable stroke which could be used to compensate at higher speeds ? perhaps the "propo...
by stew79
Tue Apr 24, 2018 4:55 pm
Forum: Tech
Topic: fork yoke dimensions or drawing.
Replies: 4
Views: 1373
Flag: Great Britain

Re: fork yoke dimensions or drawing.

hi jim, how much do you want to change the offset by, and for what purpose? as the std yokes are probably different from top to bottom, its normal practice to just alter the top figure to give you the required change. never measured b50 yokes, but gold star ones are 2.392" bottom and 2.250" top.
stew
by stew79
Tue Apr 24, 2018 9:50 am
Forum: Off topic
Topic: Crankshaft experiment
Replies: 162
Views: 26712
Flag: Great Britain

Re: Crankshaft experiment

jack, i meant the link between the throttle and the fuel valve, to try and compensate for the non linear rise in fuel requirement. the more i think about this the more i am intrigued. or do you need a fuel pump that can pump proportionally more fuel the higher it revolves ? like some thing from jet ...
by stew79
Mon Apr 23, 2018 7:36 pm
Forum: Tech
Topic: Racer intake/exhaust length &max RPM
Replies: 4
Views: 1399
Flag: Great Britain

Re: Racer intake/exhaust length &max RPM

i thought you would have had many replies to this post, but you never can tell. the inlet port size in the head sounds a bit big, ok if it reved to 10000 rpm. i cant see much use it having a vm carb over 38mm, any bigger will give terrible air flow at less than 5000 rpm and over half throttle (a pum...
by stew79
Sun Apr 22, 2018 5:04 pm
Forum: Off topic
Topic: Crankshaft experiment
Replies: 162
Views: 26712
Flag: Great Britain

Re: Crankshaft experiment

jack, i like the simple mechanical approach to the fueling, but surely as speed increases, valve timing efficiency etc gets better ? (moving more air) shouldn't the throttle link to the fuel valve be made to give a non linear opening ? (progressively opening faster for more fuel, and automatically n...
by stew79
Thu Apr 19, 2018 2:22 pm
Forum: Off topic
Topic: Crankshaft experiment
Replies: 162
Views: 26712
Flag: Great Britain

Re: Crankshaft experiment

jack, if the blower was running at 80% of crank speed, it would have a bigger pulley than the crank. in the picture the crank pulley is bigger ?
by stew79
Thu Apr 12, 2018 9:31 pm
Forum: Project bikes
Topic: B44 MX Motor
Replies: 45
Views: 7950
Flag: Great Britain

Re: B44 MX Motor

minety, i see what you mean, but the small hole diameters, rollers in the way, and small side clearance of the con rod, are all the same as many other engines. if the spinning crank of a b50 pumped more oil than the pump, this would have been spotted in the 1970,s (refer back to ccm again) it obviou...
by stew79
Thu Apr 12, 2018 7:41 pm
Forum: Project bikes
Topic: B44 MX Motor
Replies: 45
Views: 7950
Flag: Great Britain

Re: B44 MX Motor

i cant see how you could get no oil pressure at high engine speed, which could starve the rockers. if it was so, some one would have picked up on this years ago. (ccm ? ) on the my S*zuki i had to make and fit a pressure relief valve (set at 20 psi) to stop the pressure from blowing the crank oil se...
by stew79
Mon Apr 09, 2018 9:27 pm
Forum: Off topic
Topic: Crankshaft experiment
Replies: 162
Views: 26712
Flag: Great Britain

Re: Crankshaft experiment

what about that great american film "born on the fourth of July" they got the numbers the right way round, and no one noticed !
stew
by stew79
Sun Apr 08, 2018 6:16 pm
Forum: Tech
Topic: slipping kick start
Replies: 6
Views: 1378
Flag: Great Britain

Re: slipping kick start

i have the harder ccm springs and tighten them all to the same length. thats with 1.5mm of wire gap. (for the lock wire to just clear the spring cups when the clutch is pulled in). if the cups are a close fit in the hub, it will open evenly, if not replace worn parts and check the push rod isnt too ...
by stew79
Sun Apr 08, 2018 11:47 am
Forum: Tech
Topic: slipping kick start
Replies: 6
Views: 1378
Flag: Great Britain

Re: slipping kick start

hi danam, to kick over in gear, is a positive mechanical drive to the wheel. to turn the engine over is through the friction of the clutch. the "slipping" must be in the clutch, or through the tapered main shaft to the clutch center, if its loose and the key has gone. it is possible to assemble the ...
by stew79
Thu Apr 05, 2018 7:22 pm
Forum: Tech
Topic: BSA B50T Valve clearance question.
Replies: 23
Views: 3462
Flag: Great Britain

Re: BSA B50T Valve clearance question.

i am trying to look at this from an engineering point of view. setting the correct clearance, but with the engine at the wrong tdc (360 deg out) would ex plane how you could enough engine noise to fail an mot. it would result in lots of hammering at the valve seats as well. std bsa rods or better qu...
by stew79
Thu Apr 05, 2018 9:01 am
Forum: Tech
Topic: BSA B50T Valve clearance question.
Replies: 23
Views: 3462
Flag: Great Britain

Re: BSA B50T Valve clearance question.

having looked through all my text books, i cant find an index for "noisy metals". hard, soft, bendy, brittle, etc but not noisy. as noise comes from gaps between moving parts, what is needed is a volunteer with a running b50 for a scientific test. (it wont take long or do any damage to the bike) set...
by stew79
Fri Mar 30, 2018 5:35 pm
Forum: Tech
Topic: BSA B50T Valve clearance question.
Replies: 23
Views: 3462
Flag: Great Britain

Re: BSA B50T Valve clearance question.

minety, we seem to have been here before ? the spring washers are to help the valves to rotate a bit, by letting the rocker move slightly sideways. (the same as in many other different engines from different makers) perhaps if they are on the wrong end of the rocker shaft, it will rattle ? (but that...
by stew79
Wed Mar 28, 2018 2:34 pm
Forum: Tech
Topic: B50 RACER
Replies: 24
Views: 4152
Flag: Great Britain

Re: B50 RACER

nice bike, but is that a very very long ht lead from the coil / electronic igniton box ?
stew
by stew79
Thu Mar 22, 2018 5:06 pm
Forum: Project bikes
Topic: BSA B25 racing bike
Replies: 104
Views: 23690
Flag: Great Britain

Re: BSA B25 racing bike

i do like them gardener carbs, a bit like a lectron, but with the throttle cable going in the bottom. dropping the slide to open it up dose seem wrong, but they work very well, as used on all my friends racing gold stars. (thats 350 and 500) stew ps they also get unbelievable performance from there ...
by stew79
Wed Mar 14, 2018 10:00 pm
Forum: Tech
Topic: Tight mainshaft to sprocket top gear
Replies: 33
Views: 4939
Flag: Great Britain

Re: Tight mainshaft to sprocket top gear

csk holes and screws do have enough clearance (in the thread) to be slightly out of position. at this size, perhaps up to 10 thou (0.2mm ish) so not as positive as dowels. csk holes are often designed of center in components to lock parts together (a bit like some index-able carbide tooling)
stew
by stew79
Wed Mar 14, 2018 10:02 am
Forum: Tech
Topic: Tight mainshaft to sprocket top gear
Replies: 33
Views: 4939
Flag: Great Britain

Re: Tight mainshaft to sprocket top gear

it sounds like the bearing in the carrier plate is clamping axially against the shoulder of the sleeve gear, when the screws are tight. there should be a slight gap (0.020" or so) try pushing the bearing in the plate out 0.040" and see if its enough to get some clearance when the screws are tight. s...
by stew79
Tue Mar 13, 2018 8:52 pm
Forum: Project bikes
Topic: B25/TR25 Land Speed Project
Replies: 84
Views: 13741
Flag: Great Britain

Re: B25/TR25 Land Speed Project

its all looking like a very professional job, with great attention to detail. very lumpy looking piston with the coating, (thats a good idea to insulate from the heat, could you coat inside the ex port as well ?) how much bigger are the piston cut out diameters, to the valve diameters ? they look bi...
by stew79
Tue Feb 27, 2018 1:26 pm
Forum: Tech
Topic: better kickstarter for CCMs
Replies: 7
Views: 1603
Flag: Great Britain

Re: better kickstarter for CCMs

some 30 odd years ago i needed a new kick start shaft. after 2 (or3) attempts i made one, then the knuckle got too loose and bent to re pare any more. i bought a yam kick start from an rd (or xt ?) but it needed re spline-ing (19 to 20 mm with a different number of teeth) but it all works and looks ...
by stew79
Fri Feb 23, 2018 8:32 pm
Forum: Tech
Topic: B50 with Wassel ignition misfiring
Replies: 25
Views: 3676
Flag: Great Britain

Re: B50 with Wassel ignition misfiring

has any one heard from hwan recently ? thought he might have been on here recently with some of his ideas. i miss his input, even if i dont agree with him.
stew
by stew79
Fri Feb 23, 2018 3:21 pm
Forum: Off topic
Topic: Husqsa ( Bison )
Replies: 2
Views: 1199
Flag: Great Britain

Re: Husqsa ( Bison )

what a great achievement, never seen it before. but typical Swedish thing to have the ks on the left !
stew