B25/TR25 Land Speed Project

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B25/TR25 Land Speed Project

Postby koncretekid » Sun Nov 05, 2017 12:48 pm

Not having a BSA to run at Loring last year was painful, so I decided to build a B25/TR25 M class bike (Modified Stock) for laughs. The current record for the 250 M-PG class was set last year by Tracy, girlfriend of our excellent tech inspector Jesse, with a Harbor Freight 217cc motor with a centrifugal clutch at 60 some mph. I do not wish to target that excellent project, but have long felt that a properly built 250 BSA would be a good candidate for that class, and if it can exceed 92mph, would exceed every known LSR (land speed racing) record on the books. So I must apologize to Tracy and Jesse but we like to talk about "borrowing" records rather than setting them, and I'm sure they'll be back with something to challenge whatever speed I can attain.

So as I already had a TR25W frame, I visited a friend of mine and relieved him of a bunch of old parts languishing in his shed as well as some living in an old van behind his shed upon which the elements had already taken their toll. I picked up a TR25SS motor, tank, and front forks, but no wheels. Good enough for a starting point.
B25 start 1.jpg


The object of building an LSR bike to make it smaller in stature to improve wind resistance. The photos here show that I have already installed a 4" long swingarm from a CB360 H*nda that I had under the bench. I had only to make bushings for the frame to accept the smaller H*nda swing arm pivot axle and add 1 washer for spacing. This along with rear sets will allow me to scoot back further to lower my profile. The H*nda wheel will be used as well as I had it left over from my B50 LSR bike and it already has a 17" rim and oodles of sprockets.
B25 swingarm.jpg


Meanwhile, I took the head to Colorado with me this fall and flailed away at making it breath better. I cut the carb flange off, bored it out to 31mm, moved it up 3 mm, and had it re-welded in its new position (borrowing ideas from Stan and Ed). I then bored out the intake to 31.5, intending to go to 32mm, but broke through in the valve spring seat pocket. Had this welded back in and proceeded to widen the port around the valve guide until I broke thru between two of the fins! Well I filled that little hole in with JB weld, as has been suggested by others, and called it good. Did I improve the flow? I concocted a flow bench of sorts using a shop vac sucking thru a series of 4" PVC pipe with a flowmeter trapped inside and a manometer hooked up to the vacuum side so I could keep the vacuum constant as I opened the valve. I only tested the flow at 5"H2O, but the flow improved over the stock port by over 30%, so I feel it should work better than stock.

With all the work required to build a race bike, as any of you know, it seems prudent to do it well. So I ordered a bunch of new parts from Ed V. including a JE piston, Carillo rod, and Megacycle Cam. But most of the motor work will have to wait awhile for the rest of the parts: valves, tappets, valve job, and crank work, etc.

While out west (where bikes don't rust out so badly!), I picked up a nice set of CB360 forks which are 2-1/2" shorter than BSA forks, and can be adjusted up thru the upper clamps. Also, I had made some custom CNC upper triple clamps for the little Hondas in the past which are way stronger than stock, so it made sense to use one. The front wheel I stole off a Y*maha XJ650 from the same salvage yard, but did require narrowing up, losing the outer seals, and making a 9" disc to cover the hub, mostly cosmetic. It is a 17" cast wheel but only 2-1/2" wide so takes the smallest 17" tires available. It is an exact replica of the one on the B50/60 LSR bike.

I can't remember maximum size of photos so I'll try with just 2 photos.

Tom
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Re: B25/TR25 Land Speed Project

Postby koncretekid » Sun Nov 05, 2017 1:03 pm

A few more photos:

The CB350 rear wheel:
B25 with CB350 rear wheel.jpg


And the rear motor mount area. I know this has been done before, but other than Stan's $75 Ebay bike, I couldn't find any good photos. It looks like I'll have to space out the left bracket by 1/8" to match, and then make a triangular connecting bracket. The right side will require a new bracket welded to the frame along with a similar triangular connecting bracket. If anybody can direct me to photos posted elsewhere, I would appreciate that instead of having to reinvent the wheel. I'd also like to add a Norton type oil filter if I can find space. And uh oh!, there won't be much room for an oil tank when I get done, so ideas for a smaller tank would also be appreciated, as on even 3 or 4 mile runs like Bonneville, the oil won't get very hot.
B25 rear motor mount start.jpg


And here's a tickler on the cylinder head mods. I'll fill in more photos when I get that head out of boxes of stuff I brought back for Colorado last Wednesday. You can see the flange which has been bored and re-welded on in a higher location.
B25 cylinder head mods 1.jpg


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Re: B25/TR25 Land Speed Project

Postby beat » Sun Nov 05, 2017 5:18 pm

:cool: :cool: :cool:

beat :thumb

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Re: B25/TR25 Land Speed Project

Postby HPbyStan » Wed Nov 08, 2017 5:38 pm

I found a really clear photo of my rear motor mount fix BUT the damn computer won't let me cut and paste it. I've been trying different plans for three days now with no success.

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Re: B25/TR25 Land Speed Project

Postby Barry Creary » Wed Nov 08, 2017 9:32 pm

Stan get the Iresize app and reduce to about 80 percent it works for me <1011

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Re: B25/TR25 Land Speed Project

Postby HPbyStan » Wed Nov 08, 2017 11:31 pm

I'll give that a go Barry, TKS !

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Re: B25/TR25 Land Speed Project

Postby koncretekid » Wed Nov 08, 2017 11:50 pm

Stan,
Thanks for the effort, but I beat you to it. Here are a couple of photos showing new right side frame bracket and temporary mounting bracket:
B25 new right side motor mount.jpg


Back to the beginning, here a couple of photos of the front end conversion including adapters for H*nda CB360 bearings to the BSA frame. The H*nda triple clamps are odd sizes, 26.5mm x 48.5mm, and 30mm by 50mm, and the stem is longer so the adapters had to have some height as well. The CB360 forks cleaned up real well, especially with the CNC top triple clamp.
B25 steering bearing adapters.jpg
B25 new front XJ650 wheel.jpg
B25 right side new motor mount - A65 pipe.jpg
B25 left side with front end.jpg
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Re: B25/TR25 Land Speed Project

Postby Victor500T » Fri Nov 10, 2017 10:35 pm

Is the 92mph target serious? Just curious.

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Re: B25/TR25 Land Speed Project

Postby koncretekid » Sat Nov 11, 2017 9:05 pm

SCTA record for 250cc pushrod motor on gasoline was set in 2010 at 94.194 mph on a BSA! I have no idea what this one will do as I have never had a B25 before. AMA record is a little less intimidating at 82.541 on a modified Triumph cub.
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Re: B25/TR25 Land Speed Project

Postby Victor500T » Sat Nov 11, 2017 11:25 pm

Only wondering because - from near-childhood memories of riding a quick B25 - I'd expect well over 90mph to be possible with clip-ons and a small fairing, with a pretty much standard engine. I out-ran a police car, two up, with the gearchange lever splines buggered and not possible to go higher than 3rd gear when I was 17. Must have been revving to 9000+!

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Re: B25/TR25 Land Speed Project

Postby minetymenace » Sun Nov 12, 2017 12:47 am

The difference is between altitude and attitude. :grin:
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Re: B25/TR25 Land Speed Project

Postby koncretekid » Sun Nov 12, 2017 12:52 pm

Victor500T wrote:Only wondering because - from near-childhood memories of riding a quick B25 - I'd expect well over 90mph to be possible with clip-ons and a small fairing, with a pretty much standard engine. I out-ran a police car, two up, with the gearchange lever splines buggered and not possible to go higher than 3rd gear when I was 17. Must have been revving to 9000+!


So you seem to be saying that you think speeds in excess of 90 mph are possible, even though I am no longer 17 and the police won't be after me? That's encouraging. My B50 road race bike, with JE piston and Megacycle cam reached 108 mph on my first trip to Bonneville with about 35 rear wheel hp.

So who has the fastest B25 on this forum, or knows of a very fast one? And what is the highest rear wheel hp that anyone has heard of? What other tricks of the trade for performance?

Tom
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Re: B25/TR25 Land Speed Project

Postby hwan » Sun Nov 12, 2017 1:01 pm

106 mph through the IOM speed trap on a C15 this spring.

I say C15 - it has a B25 top end on it, and i say IOM, it was actually the Southern 100 course which doesn't have the big long straights and hills.
Was lieing 7th behind a few Aeromacchi/Ducati's before an oil leak stopped him - 65 years old, first time @ IOM, last raced +20 years ago.

Was heavily #looked over' in the paddock as it was the only four-stroke britbike in the 250 class, hopefully hes going next year.

The bottom end is C15 which has allowed him to make a very easy remove cover to change cams - he is currently running a genuine MX cam, which is giving him a lot of megophonitus - i'll contact him and see what its doing on the dyno and where he is with it.

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Re: B25/TR25 Land Speed Project

Postby Victor500T » Sun Nov 12, 2017 10:48 pm

koncretekid wrote:So you seem to be saying that you think speeds in excess of 90 mph are possible, even though I am no longer 17 and the police won't be after me?


You should be able to get a police car on your tail if your try it on the road. At a more mature age though, the biggest obstacle to maximum performance is common sense!

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Re: B25/TR25 Land Speed Project

Postby koncretekid » Tue Nov 14, 2017 6:20 pm

Victor500T wrote:You should be able to get a police car on your tail if your try it on the road. At a more mature age though, the biggest obstacle to maximum performance is common sense!


And I bet he could tell me how fast I was going too! Good idea!

But I have another question. Most of the sources tell me that the maximum hp occurs on a stock B25 at 7250 rpm, but I seem to remember at least one source that quotes maximum hp at 8250 rpm. Which is correct? I know I can boost the max hp rpm by 1000 rpm, but I'm looking for a starting point to determine gearing. I usually gear for max hp rpm at the lights.

B25 frame as painted.jpg

I've disassembled and painted the frame. I was tempted to cut off the footpeg mounts and the kick stand mounts but decided I can do that later if they pose a problem. So far, the only mods to the frame are the motor mounts for the later motor. Procedure for painting is about 2-3 hours of paint stripper and scraper followed by an hour of sandblasting with 1-1/2 bags of single ought (0 grade) sandblasting sand. Paint is lacquer based primer with acrylic enamel finish.
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Re: B25/TR25 Land Speed Project

Postby hwan » Tue Nov 14, 2017 7:02 pm

till cannot post bloody pix!

C15 is pulling 8500 rpm using MX cam - supposed to be limit for the roller bearing/long rod crank, but so far ..................
Oh yes, its got a KH250 clutch fitted to a machined C15 chain-wheel, simple lever type Clutch push-rod activation (common UK grass-track mod) and standard B25 valve sizes.
He found that with a lot of closing down clearances, he achieved 11:1 using a standard B25 postilion (he runs petrol).

When building a RR 250 engine for myself, i discovered a 8:1 C15 piston, in a B25 head gives ~10:1 and a 9.5:1 piston gave 11.5:1 - before cutting back all the valve cut-out ridges, etc.
The only problem is that the valve angle of the C15 is 90deg, the B25 is something less - many high CR C15 pistons have enough metal in them to safely re-cut the piston cut-away angle.

Max inlet-valve i coaxed into the standard bore B25 is 43.5mm (A65 inlet - machined) - anymore and it hits the top edge of the liner.

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Re: B25/TR25 Land Speed Project

Postby Chris Pellett » Tue Nov 14, 2017 8:13 pm

Red line was 8200rpm but in tearaway years I always found power bands were at 4200-4500rpm and again at 8500-9000rpm hence short engine life.
With a worn out MX camshaft (deliberate for reduced lift) and Omega piston, keeping up with Yam and S*zuki two strokes was easy while it lasted.

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Re: B25/TR25 Land Speed Project

Postby Victor500T » Tue Nov 14, 2017 10:55 pm

https://www.ebay.co.uk/itm/Rare-BSA-C15 ... 2094760304

This looks like a book to look out for.

There's a website somewhere with loads of tips on tuning B25 engines. I'm sure I will have save a link - just a question of finding the link! I've met a few people at classic/vintage race meetings who've been racing B25s and C15s. Must admit, not with much success against the Ducatis and Hondas. But I know from experience that they can go surprisingly well, if only for brief periods!

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Re: B25/TR25 Land Speed Project

Postby Canberra » Wed Nov 15, 2017 10:55 am

How modified can you go with the engine? Stan <1011 managed 11K rpm out of his B25 :shock: but no idea how much was usable for a speed attempt gearing.

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Re: B25/TR25 Land Speed Project

Postby koncretekid » Wed Nov 15, 2017 12:58 pm

In Land Speed Racing, we are only limited in the size of the motor. AMA does not allow any oversize, while SCTA and Loring allow .020" oversize even if it puts the motor over the class limit. This is a pushrod only class, so no OHC Hondas or desmo Ducatis or 2-strokes.

I know these motors have been known to survive very high rpm, but where is the max hp rpm? I gear for the max hp rpm to achieve my fastest speeds at the timing lights. If the max hp rpm is 8500, I gear for that. If I gear too high, it won't get there. If I gear too low, it peaks out and will stop accelerating after the peak.

I've tried twice to post a couple more images this morning, but my internet is too slow.

Tom
Last edited by koncretekid on Wed Nov 15, 2017 4:00 pm, edited 1 time in total.
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Re: B25/TR25 Land Speed Project

Postby koncretekid » Wed Nov 15, 2017 3:58 pm

I'll see if my internet is back up. Here are a couple of photos of my cylinder head as ported to about 31.5mm:
B25 head right side.jpg

B25 ported head 2.jpg

Flow seemed to improve at least 25% with my crude flow bench at 5" H2O.
Last edited by koncretekid on Fri Nov 17, 2017 2:16 am, edited 1 time in total.
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Re: B25/TR25 Land Speed Project

Postby hwan » Wed Nov 15, 2017 4:18 pm

On my own flow-bench, the flow velocity on the floor of the port was very low, using various blobs on wire, i think its indicating that the cylinder wall is seriously compromising flow around the valve head.

My bored out (75mm bore) cylinder more or less confirmed this, with much better velocity/flow-rates - though i have no numbers, just comparative pressure drop/flow-rates - i must admit i lost interest at this point and have done no more work on the B25.

I suspect your down-drafting of the port is helping give the +25% improvement.

I raced a BMW flat twin outfit, the inlet port on these is basically shaped like a question mark, so the carbs point towards the crank center-line (to keep them out of the way of the riders feet) - i 'down-drafted' these heads ~15deg from the gasket surface, with DRAMATIC power improvements.
Such that the outfit became a wheelie monster, needing the passenger to get to the front for the 'chair' as soon as it fired (push start) otherwise i would go off at a tangent cos the front wheel was off the ground :shock:

Going back to what rpm - certainly my B25 would rev to 10K in the lower gears, of my MX bike - it did have a big-rod a std piston and EV recommended oiling mods.
Since i have fitted a C15G roller b.e. crank, it dosnt rev as well, but then again i suspect my cam timing is not retarded as it was (std B25 cam).

Talking of oil and oil-pressure - make sure you get the higher flow-rate CI pump, there are two distinct versions - though you probably know this already :grin:

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Re: B25/TR25 Land Speed Project

Postby Victor500T » Thu Nov 16, 2017 12:00 am

Trial and error probably work better than attempting to figure it out on paper. I'd experiment with different carbs, exhausts (lengths as well as types), valve timings, comp ratios, final drive gearings etc until I arrived at what I felt best for the purpose. Having said this, such an approach is fine with engines such as Triumph & Norton twins, or even B50s, but with a B25, you could wear the thing out before arriving at the optimum settings!

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Re: B25/TR25 Land Speed Project

Postby stew79 » Thu Nov 16, 2017 10:23 am

i have always used the trial and error method for looking for more performance. (but with careful attention to detail, and recording whats been changed) but a b25 cant be too fragile ? is it ? it only takes 2 mins of running up the road (or track) to confirm if the latest mod is working or not, no point thrashing on if it aint right.
stew
ps had an old yam yz scrambler registered for the road with 1978 250 H*nda xl engine (daily commuter bike, play bike etc) occasionally went on the dyno just to confirm what it was putting out. 24 hp with std cam (good bottom end pull) or 27 hp with cam from rs250 road bike (not quite as much bottom end but stronger from mid range upward. same max rpm about 10000, although no point going over 9000 as it flattens off with both cams) thats on super unleaded petrol

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Re: B25/TR25 Land Speed Project

Postby stew79 » Thu Nov 16, 2017 10:32 am

found a pic of old bike
Attachments
DSCF2868.JPG

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Re: B25/TR25 Land Speed Project

Postby koncretekid » Fri Nov 17, 2017 2:13 am

Stew,
Those old 4 valve Hondas were as good as the 4-strokes got in their day.

Thanks for all advice on the motor. I think I'll gear for about 90 mph at 8500 rpm for starters with sprockets either side of that, as I think the max hp will be somewhere around there.

I put the wheels and front end back on to make it a roller, as it may be awhile before I get the motor done. I stripped the cases this PM and found them acceptable with some not-so-nice welding repairs to the primary side screw bosses, but it will work. Biggest set-back for now is that the crankshaft appears to be about .011" undersize, so has been ground down. I have another crank in Colorado and I'll be flying there for Christmas - - just have to figure out how to bring it back in my carry-on bag.
B25 cases cleaned primary side.jpg
B25 crankshaft 1.jpg

Note on the front wheel that I traded the spoke wheel I had on the Bridgestone with the new Y*maha cast wheel to get both spoke wheels on this one. It's a 17" x 1.85 San Remo high shouldered rim with Buchanan's SS spokes so shows up well. Don't know about that tank though, as it's quite high so I might have to substitute for another tank that I have. As it sits, the frame is now about 5" off the ground, but could go lower with shorter rear shocks or rigid struts.

B25 painted with wheels.jpg

Tom
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Re: B25/TR25 Land Speed Project

Postby midgie » Fri Nov 17, 2017 8:54 am

The crank looks like the early type, as the conrod relieve in the later type is longer. but I could be wrong!

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Re: B25/TR25 Land Speed Project

Postby stew79 » Fri Nov 17, 2017 9:35 am

the standard old 250 hondas were not very powerful, but smooth and reliable. just waiting to be tuned up a bit. every thing that worked on making it faster, would transfer over to a bsa 250.
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Re: B25/TR25 Land Speed Project

Postby stew79 » Mon Nov 20, 2017 12:27 pm

tom, the rolling chassis is looking very good, but any development with the engine ? still waiting for any one to publish any dyno figures for a 250. how much better is methanol over petrol ? 10 years ago a local garage sold proper 4 star with lead. this was noticeably better than super un leaded in my bikes, but they stopped selling it. (under ground tank too small for minimum delivery)
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Re: B25/TR25 Land Speed Project

Postby koncretekid » Mon Nov 20, 2017 10:32 pm

Stew,
Thanks for the compliment. There has been no other motor development due to not having a good crankshaft. It will have to wait until I get back from Colorado Jan 4th at which time I hope to have new valves as well. Even then, I have to drive 150 miles to get a good valve job done and look for a few missing parts.

In the meantime, I'm adding rear suspension to my B50 600cc Land Speed Bike which is another major project. I expect to post that work on landracing.com and will post a link when I've done that.

Here is an interesting link to a supercharged B25 land speed project that took place in Colorado Springs, CO which even I did not know about.

http://www.bmacinc.com/wp-content/uploa ... y-2017.pdf

Tom
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Re: B25/TR25 Land Speed Project

Postby stew79 » Mon Nov 20, 2017 11:48 pm

hi tom, you have a busy scheduled, but any thoughts on using a completely different piston in the 250 ? (xs650 for example ?) with a pressed up crank and roller bearing ? the stroke could be made to give 249cc with more strength than a plain big end. (normal lower pressure oil pump etc) it seems the std piston to com, chamber is not too good, with a different piston and perhaps some welding and re shaping in the head it could work better ? as for the super charged bike wow, what a lot of work. there must be quite a lot of potential in that project, but a bit disappointing results ( i blame the dam electronics ! should put a carb on the inlet to the blower, old fashion style)
stew

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Re: B25/TR25 Land Speed Project

Postby koncretekid » Wed Dec 06, 2017 9:53 pm

I promised the link to my rigid to single shock conversion on partial streamliner so here it is: http://www.landracing.com/forum/index.p ... 962.0.html

stew79 wrote:hi tom, you have a busy scheduled, but any thoughts on using a completely different piston in the 250 ? (xs650 for example ?) with a pressed up crank and roller bearing ? the stroke could be made to give 249cc with more strength than a plain big end. (normal lower pressure oil pump etc) it seems the std piston to com, chamber is not too good, with a different piston and perhaps some welding and re shaping in the head it could work better ? as for the super charged bike wow, what a lot of work. there must be quite a lot of potential in that project, but a bit disappointing results ( i blame the dam electronics ! should put a carb on the inlet to the blower, old fashion style)
stew


Stew,
First off, I am using a late model B25/Tr25 motor and it has the correct iron oil pump and I will be adding an oil filter as well. Your ideas are well taken, but since we only get one or two chances per year to try out our land speed bikes, we have to make choices in the build of the motor and just make jetting and timing changes at the meets. That's why we have forums so we can try to find out what others have successfully campaigned in the past. I've looked very seriously at a B40 crank to see if the crank pin could be relocated to give a shorter stroke. At around 63mm, what a screamer it would make and would also work in a B50 motor to make a hot 350. At least the BSAs have a better (shallower) combustion chamber design than the Triumph twins and triples, so they are reasonable. We shoot for the highest compression ratio possible, especially at Bonneville because the low atmospheric pressure at 4400 feet altitude allows higher C.R. I measured my 600cc B50 motor at 14 to 1, but that may not be exact. We have to use the "event" gas unless we want to run in "fuel" class and then we can run whatever we want to. I use 110 octane at Bonneville, and slightly higher at Loring and with dual plugs, I've not had any pre-ignition or detonation problems using a ceramic coated JE piston so I'll start with that for the B25 (don't know the C.R. yet). I haven't decided on a carburetor yet, but those $35 Keihn replicas form China are tempting. Or I may just start with a 32mm Norton Amal which I have (used). At wide open throttle, I don't see why it won't work.

As for the supercharged B25 from Colorado, I would say they have a lot of potential but just wanted to break it in on lower boost. I expect faster runs from them in the near future.

Tom
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