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Author Topic: STD 250 APS/PF for 2011  (Read 4282 times)
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WhizzbangK.C.
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« on: July 15, 2011, 08:44:55 PM »

Some may remember this bike from last year, and the trials and tribulations I've experienced with piston seizure. First year I though it was jetting, second year I thought it was oil starvation, last year it happened again, and when I pulled out the galled piston it was dripping with oil and no sign of lean condition on the head. Quite frustrating, to say the least, and my pile of toasted pistons has grown to a depressing level.

This year I've done a lot of looking back at what's happened and what I've done wrong, and possibly done wrong. I came to the conclusion that I started this journey with several problems, everything that I though was a problem in the past actually was, I was only addressing the most obvious things as they appeared, and not looking deeper for other existing conditions.

As you may recall, the engine on this bike is buried inside the body work. It is a 1971 Triumph TR25W, single cylinder 250cc push rod 4 stroke. I'm running 12.5:1 compression with a Megacycle cam retarded for more top end oomph. The engine was initially built with all the tolerances set up tight, this included cylinder clearance. I now believe that this was the last major oversight in my planning, since I failed to take into account that the piston might expand more than the jug due to compromised cooling.  embarassed

To address this, I've honed the cylinder out to provide .0055 clearance cold, up from the .0030 that I have been running. I've also built some quick and dirty cooling shrouds to direct more of the air flow from the electric fan across the cylinder and head to help prevent overheating. My hope is that these mods will finally kill the gremlin that has been chasing me every since I started running this thing.  cheesy

One other thing I've done is to add a catch tank to the oil tank vent. Last year I was mortified to get back to impound with the truck and tools and discover that the bike had been dripping oil onto the salt. Some kind person had found a card board box to put under it to catch most of the oil. A major oversight that should not have happened on my part. Belated thanks to who ever it was that took care of the problem and didn't even bother to chew me out for it.  embarassed

Anyway, due to other obligations and short funds, these are the only mods I'm doing for this year, the wood body work stays for now, no new front fairing, nothing visible and cool looking added. At least the bike proved itself stable and easy to ride last year. The hope is that this year the engine will hold together and I'll be able to get in a lot of good runs, bump the record some more, and not have to do any on the salt McGuyver type repairs to salvage the week. LOL.

Not much new to see, but here's a short vid of the second start up, in case anyone's interested. It sounds much better in person. Pretty good for a 250 I think!

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Stan Back
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« Reply #1 on: July 15, 2011, 09:17:43 PM »

Sounds Dodge good for a 250!

I like the idea of the battery doubling as a tachometer, too.

Stan
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« Reply #2 on: July 15, 2011, 10:11:12 PM »

Stan,  I thought you of all people knew that before the invention of the British single cylinder engine vibration didn't exist.

Ed.  You gotta have air flow over the cylinder.  Most vital!  Get cool air flowing over the cylinder and you'll never have another piston problem.
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WhizzbangK.C.
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« Reply #3 on: July 15, 2011, 10:34:41 PM »

Yeah, I forgot to get the batteries tied down before I started it, been a long time and just wanted to be sure it was going to run.  cheesy

As far as air flow, the first frame had the engine out in the open, but I had major self induced carb issues, and oiling problems. Last year I had the fan in front of the engine, blowing over it, but nothing to direct the air flow against the cylinder and head fins. The tins that I made for this year are the result of a lot of cut and tape experiments with card board. Even though the entire back half of the cylinder and head are outside the tins, the air flow wraps around them nicely, and there is no spot on them that doesn't get a  good air flow. I think that with this addition and the extra clearance on the piston I have the gremlin whipped. At least I hope so. I let the engine run for over 5 minutes, then shut it down and measured temp all around the cylinder and head with my infra-red thermometer, the temps were very even and surprisingly low.
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« Reply #4 on: July 16, 2011, 10:56:52 AM »

Ed, are you using a contact breaker (points) ignition trigger? 
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WhizzbangK.C.
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« Reply #5 on: July 16, 2011, 02:54:56 PM »

Ed, are you using a contact breaker (points) ignition trigger? 

No, I'm running a Boyer Bransden MkIII. Why do you ask, Bo?
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octane
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« Reply #6 on: July 16, 2011, 03:13:39 PM »

... here's a short vid of the second start up, in case anyone's interested...
I am !
Sounds good.

Glad to hear you're coming this year. Thought you wouldn't be.
Looking forward to see you again.

.
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WhizzbangK.C.
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« Reply #7 on: July 16, 2011, 03:25:32 PM »

... here's a short vid of the second start up, in case anyone's interested...
I am !
Sounds good.

Glad to hear you're coming this year. Thought you wouldn't be.
Looking forward to see you again.

.

Well Lars, it's like this. I promised the wife a "together" vacation this year to somewhere with white sandy beaches and cool ocean breezes, so my thinking was I can't afford both trips. Then, her nephew got engaged to a Japanese gal. The wedding is in Hawaii, first week of August. My sister-in-law, nephew's mom, insisted we attend and is paying air fair and hotel for us to go. Magically, the expense of the vacation dropped to almost nothing, so I can afford Bonneville this year also!!!

Here's hoping both our engines hold together for some good runs this year. As much as I enjoyed hanging out in the pits with fellow broken motor sufferers, I'd much rather be on the course as much as possible.

See ya there!!!
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WhizzbangK.C.
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« Reply #8 on: July 16, 2011, 06:17:48 PM »

I find myself in a very unfamiliar situation. The engine is done, test ran, heat cycled, re-torqued everything, all final checks, adjustments, and tuning done as much as possible till we're actually on the salt. I've decided not to make any modifications to the body at all so that I can be certain that any improvements are due to the engine mods. Already double and triple checked everything, safeties, clamps, bolts, wheel bearings, tire pressures, chain adjustment, cables, hoses, wires. Only thing left to do is bolt the body on, takes about 1/2 hour.

It's still 6 weeks till fun time. What am I supposed to do with all this time?Huh? It'll take one day to pack up the bike, tools, and spares since all that stuff is already staged to go into the trailer. What the fark am I supposed to do with all this spare time??? I'm going to go stir crazy here without a last minute thrash to keep me occupied.

Does any one have any experience with this that could possibly offer some suggestions???
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« Reply #9 on: July 16, 2011, 08:28:13 PM »

Spend some time patting yourself on the back.
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WhizzbangK.C.
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« Reply #10 on: July 16, 2011, 08:36:19 PM »

Spend some time patting yourself on the back.

LOL, naw, I'm done with that now. Just having a little fun at my own expense. I do still need to check and pack the trailer bearings, get some E-track installed in it, organize the tools so that we'll be able to find them, change the oil on the truck, inventory spare parts and make sure they all get loaded, go on vacation with the wife for a week, etc. You know, all the stuff that I've never had time to do right because I've always been in a mad thrash to the last second just to finish the machine. Hell, last year I spent the first 2 days on the salt getting it running for the first time. I have literally never in my life been done with anything with time to spare, so this is new territory for me.  cheesy
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wobblywalrus
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« Reply #11 on: July 17, 2011, 12:55:47 AM »

Ed, this is based on experience with similar BSA engines.  The spark advance and point cam are at the end of the valve cam that rides in bushings.  I am sure you have seen it many times.  Often the bushings wear and the point cam wobbles.  This upsets the timing and can cause problems like you describe.  The solution was to renew the bushings so there was less wobble and to install an electronic ignition.  You have done this.

Years ago I gave away all of my British tools and manuals when I switched careers.  One of the few souvenirs I kept was my BSA B25 book.  One thing I highlighted was the note telling me which way to install the connecting rod.  There is an oil hole in it on one side.  As I recall, there can be lubrication problems if the rod is backwards.  The oil that lubes the inside of the cylinder flies off of the rod big end.

Sometimes a racing Morgo oil pump will help.  One of my favorite modifications is a new or improved pump with a lighter viscosity oil such as 10W-40 or 20W-40 instead of the commonly used 20W-50.  First, I put on a gauge to read the oil pressure and then I try a lighter oil.  I use the lighter oil if the oil pressure is acceptable.  My reasoning is that I get greater flow volumes through the motor with the thinner oil and cooling and lubrication will be improved.

   

 
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Unkl Ian
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« Reply #12 on: July 17, 2011, 12:11:33 PM »

Does the body work have an opening to air air to get into the fan ?
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« Reply #13 on: July 17, 2011, 03:06:52 PM »

... here's a short vid of the second start up, in case anyone's interested...
I am !
Sounds good.

Glad to hear you're coming this year. Thought you wouldn't be.
Looking forward to see you again.

.

Well Lars, it's like this. I promised the wife a "together" vacation this year to somewhere with white sandy beaches and cool ocean breezes, so my thinking was I can't afford both trips. Then, her nephew got engaged to a Japanese gal. The wedding is in Hawaii, first week of August. My sister-in-law, nephew's mom, insisted we attend and is paying air fair and hotel for us to go. Magically, the expense of the vacation dropped to almost nothing, so I can afford Bonneville this year also!!!

Here's hoping both our engines hold together for some good runs this year. As much as I enjoyed hanging out in the pits with fellow broken motor sufferers, I'd much rather be on the course as much as possible.
LOL...me too !

Quote
See ya there!!!

See ya' Ed !
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not when there is nothing left to add
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WhizzbangK.C.
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« Reply #14 on: July 17, 2011, 04:03:21 PM »

Ed, this is based on experience with similar BSA engines.  The spark advance and point cam are at the end of the valve cam that rides in bushings.  I am sure you have seen it many times.  Often the bushings wear and the point cam wobbles.  This upsets the timing and can cause problems like you describe.  The solution was to renew the bushings so there was less wobble and to install an electronic ignition.  You have done this.

Years ago I gave away all of my British tools and manuals when I switched careers.  One of the few souvenirs I kept was my BSA B25 book.  One thing I highlighted was the note telling me which way to install the connecting rod.  There is an oil hole in it on one side.  As I recall, there can be lubrication problems if the rod is backwards.  The oil that lubes the inside of the cylinder flies off of the rod big end.



Sometimes a racing Morgo oil pump will help.  One of my favorite modifications is a new or improved pump with a lighter viscosity oil such as 10W-40 or 20W-40 instead of the commonly used 20W-50.  First, I put on a gauge to read the oil pressure and then I try a lighter oil.  I use the lighter oil if the oil pressure is acceptable.  My reasoning is that I get greater flow volumes through the motor with the thinner oil and cooling and lubrication will be improved.

   

 

Yep, I know which oil hole you speak of, it's supposed to point to the left side of the engine. I'm running a steel Carillo rod. It does not have that hole in it. I asked Ed Valiket (E&V Engineering, he does a lot of the most competitive BSA and Triumph singles out there) what the purpose of the hole was and if it would be advisable to add one to the Carillo. His answer was that the hole was there to ensure adequate lubrication to the left side crank bearing, and assured me that there was no issue with not having the hole on the Carillo rod, as it gets plenty of oil without it. Also without the hole it keeps the oil on the journal longer. I'm taking him at his word on this as he has a lot of these engines out there running road races with similar set up and no issues.

As you surmised, the cam bush has been replaced, and I don't have any issue with wobbling shaft, or at least the bike doesn't.

The B25/TR25 uses a positive displacement gear pump. I was unable to find an aftermarket pump for it, high flow or otherwise. It is the same pump that was used in the twins though, so should provide plenty of flow and pressure for this application, with a lot less leak points internally to cause pressure drop. I did take it all apart and make sure everything was to tolerance.

Thanks for the "looking out" and if there's anything else that you can think of, let me know. I'm certainly not any kind of expert on these things, and will take any advice that I can get.
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