Author Topic: RD250 A/B with LC350 barrels  (Read 497 times)

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Offline Richard S

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RD250 A/B with LC350 barrels
« on: May 22, 2020, 07:48:05 PM »
Hi ,I have always wanted to build a air cooled RD with LC barrels, l have a spare A/B engine, do LC350 barrels fit ,anyone with any information would be great. Thanks Richard

Offline D Peacock

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Re: RD250 A/B with LC350 barrels
« Reply #1 on: May 22, 2020, 08:14:17 PM »
Crankcase mouth and stud layout is the same, you may need to mix and match studs and bolts but yep everything pre YPVS will swop.
For speed add lightness!

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Offline 5port

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Re: RD250 A/B with LC350 barrels
« Reply #2 on: May 22, 2020, 08:29:11 PM »
Hi Richard!  I was doing this conversion but, I decided to change to aircooled 350 for my trackbike.  The LC cylinders and heads roughly fit on the cases but, here are the complications I found, other than using the correct parts to suit...   The cylinderstuds and headbolts need to be 350LC.  The liner extensions into the cases might need shortening to fit fully into the cases and, the piston top deck-height and squish will need setting.  You need to decide how your cooling system will be, in detail.  For the track, I was looking at using a 12V waterpump.  You could try to modify an LC sidecase and mechanical pump but, the detail is complicated.  The route for the waterpipe from the cases to the head is not simple. 
Good luck with it!  :)

5port
   
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Offline Richard S

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Re: RD250 A/B with LC350 barrels
« Reply #3 on: May 22, 2020, 08:37:15 PM »
Hi ,nice to hear from you 👍I will have a go ,I have always wanted to do this ,I have got a Daytona rolling chassis and a A/B engine, was going to put a 400 in but changed my mind. Keep you updated. Richard

Offline gordon moore

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Re: RD250 A/B with LC350 barrels
« Reply #4 on: May 22, 2020, 10:26:58 PM »
Hi I have built a special with a farhon engine tz750 barrel on rd400 crankcase something different.
Gordon

Offline Cooper

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Re: RD250 A/B with LC350 barrels
« Reply #5 on: May 22, 2020, 10:33:06 PM »
Gordon You're an artist!

Offline Richard S

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Re: RD250 A/B with LC350 barrels
« Reply #6 on: May 23, 2020, 07:43:04 AM »
Yes I would be pleased with that,very nice work . :) by the way any body been watching Alan Miillyard home videos.
« Last Edit: May 23, 2020, 07:46:14 AM by Richard S »

Offline elliottles1

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Re: RD250 A/B with LC350 barrels
« Reply #7 on: May 23, 2020, 08:49:56 AM »
folks,

ive done it, 250 lc barrels are easier by virtue of the fact that you do not have to reduce the liner insert tangs. they go straight on albeit with longer studs. plus 350 barrels are rare as rocking horse poo and v. expensive.
plumbing using a 50 quid bosch electric water pump is a doddle.

https://www.youtube.com/watch?v=G6nvu7NVj-k

cheers
les
« Last Edit: May 23, 2020, 08:57:33 AM by elliottles1 »

Offline c50

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Re: RD250 A/B with LC350 barrels
« Reply #8 on: May 23, 2020, 10:49:25 AM »
folks,

ive done it, 250 lc barrels are easier by virtue of the fact that you do not have to reduce the liner insert tangs. they go straight on albeit with longer studs. plus 350 barrels are rare as rocking horse poo and v. expensive.
plumbing using a 50 quid bosch electric water pump is a doddle.

https://www.youtube.com/watch?v=G6nvu7NVj-k

cheers
les

Result is a RD250E, porting is identical although the LC benefits from better exhausts and a leaner mixture (well, and a far better bike) . With a set of LC exhausts, air box and carbs it would be the same. Ditto for a 250E but it would probably seize through lack of cooling.

Offline tony2stroke

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Re: RD250 A/B with LC350 barrels
« Reply #9 on: May 23, 2020, 12:08:08 PM »
folks,

ive done it, 250 lc barrels are easier by virtue of the fact that you do not have to reduce the liner insert tangs. they go straight on albeit with longer studs. plus 350 barrels are rare as rocking horse poo and v. expensive.
plumbing using a 50 quid bosch electric water pump is a doddle.

https://www.youtube.com/watch?v=G6nvu7NVj-k

cheers
les

Whats that plant on the table

Offline chrisg.007

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Re: RD250 A/B with LC350 barrels
« Reply #10 on: May 23, 2020, 02:00:28 PM »
LC350 cylinders aren't cheap, so maybe consider fitting a 250LC with 350 cylinders or 350LC engine. All the cooling and is sorted and the cylinders fit without machining. Just a thought.


Personally I would consider a YPVS engine (60bhp). I think that you have to fit the loom as well to get the servo to work. Sound like a project  ;)
Growing old is compulsery, growing up is optional.

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Offline elliottles1

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Re: RD250 A/B with LC350 barrels
« Reply #11 on: May 23, 2020, 03:37:28 PM »

the things people spot.

long time ago now, I think it was an ash sapling. I have its mum and dad outside.

les

Offline 5port

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Re: RD250 A/B with LC350 barrels
« Reply #12 on: May 23, 2020, 04:58:58 PM »
Yes, the cost is getting high to do the LC cylinder mod to an aircooled.  I had planned to use a TZ primary case and waterpump.  That works well but, the availability and cost of those are now difficult.  Unless you are lucky to have the TZ parts, you really are looking at an electric waterpump.  I decided that it should be fairly straightforward to get 50bhp, or so, out of a 350 aircooled for the track and, it should be a bit lighter without the rad, pump, pipes, battery and....water!  ;D
So, that is where I am now.

5port   
5port

Offline elliottles1

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Re: RD250 A/B with LC350 barrels
« Reply #13 on: May 23, 2020, 05:16:23 PM »

weight was partly why I used an alloy chassis, the finished bike weighs 25kg lighter than a 250lc, one sack of cement.
the electric water pump is really easy and effective, runs permanently with the ign. on. a lot more straightforward than converting a tz pump, and cheaper.

les

Offline tony2stroke

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Re: RD250 A/B with LC350 barrels
« Reply #14 on: May 23, 2020, 05:35:32 PM »

the things people spot.

long time ago now, I think it was an ash sapling. I have its mum and dad outside.

les

I am just playing mate  :D :D :D :D