Tuning a Mototrans 250cc

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NewKidOnTheBlock
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Re: Tuning a Mototrans 250cc

Postby NewKidOnTheBlock » Sun May 18, 2014 11:46 am

Cheers for the ebay link Jon, I'd seen that one on there but I had no idea what it was from or whether it'd be better or not compared to what I have already? Eldert - thanks for the tip, I've tried phoning Phil Joy already as he has no online presence I can find but the phone hasn't been answered yet, I will try again next week in hope!

DewCatTea-Bob
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Re: Tuning a Mototrans 250cc

Postby DewCatTea-Bob » Sun May 18, 2014 11:53 am

[quote= NewKidOnTheBlock ...
" The Moto trans head as I received it has as 23.6mm dia. inlet (measured where the manifold bolts on) and was fitted with a 32mm inlet valve and a 30mm exhaust valve, "

____ Wow, I can't hardly believe that a 250-head (with a 69mm-bore) would have such small valve-heads, (even smaller than a 200 with a 67mm-bore) ! _ Seems more suited for a 175 (with a 62mm-bore).
Furthermore, it seems unDucati-like & strange to match-up such small valves & OVERLY-small intake-port with a camshaft which supposedly has such wild valve-timing !
__ When you bought the 250-Mototrans motor, was it complete or reduced to various parts ?
How about some pictures of the supposed 250 cyl.head ?



" The cam fitted to the mototrans head has 25mm base circles on both lobes, inlet measured 32mm at the peak and exhaust measures 32.2mm at the peak. "

____ That gives you cam-lobes with merely-just 7 & 7.2mm of peak-height,, which, (while well suited to the valve-sizes you measured), is not only rather small for a '250', but also somewhat nonsensical matched-together with a camshaft that has wild valve-timing (which your engine-model is supposed to have).
__ The intake-lobe ought-to be the tallest, do you realize that the exhaust-lobe is the one that's located on the LEFT-side ?



" The 'spare' head I have which housed my mystery cam has a 36mm inlet valve and 33mm exhaust,
It has a inlet to the head of 28mm from the manifold, "

____ That seems to be a std.250 head.
Have you noted that it's cyl.bolt pattern is rather wider than the square-pattern of the Mototrans-head ?



" the cam fitted to that, my 'mystery' cam has a base circle of 24.4mm, inlet peak of 32.2mm and exhaust peak of 32.1mm. "

____ That gives you lobe-lifts of 7.8 & 7.7mm, which is fairly consistent with a White/Scrambler-cam !



" I was sold the head as a 'scrambler' head hoping to use the cam but from the measurements I don't believe the cam was a scrambler part although the rest of the head seems to match. "

____ It seems you were told correctly that your spare-head is a 250-Scrambler item. _ But what makes you think it's camshaft wasn't,
what 'measurements' were you expecting it to have (any different from that which you discovered) ??



" I would like the engine to provide as much useable power as reasonably possible without loosing reliability "

____ I'd say a camshaft which has specs somewhere between that of a White-cam & a Red-cam, would be in the ball-park for you then.



" or spending a fortune on it. "
" The cost for 2 lobes is £100+VAT, so £120. This comparing to £280+VAT = £336 for a new reproduction cam "

____ Aren't any of those costs what you'd call a "fortune" ?



" This photo is of the cam taken from the bearing support end, "

____ Then that shows the cam-lobe of the exhaust-side.
__ Which camshaft is it, the Scrambler-cam ??
It's profile is-not that of a 'wild-cam', yet it's peak looks a little flat for a regular White-cam,, and-also, it's base-circle is that of a n-c.version.
__ I've posted an altered version of your pic, below.


Duke-Cheers,
-Bob
You do not have the required permissions to view the files attached to this post.
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob

NewKidOnTheBlock
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Re: Tuning a Mototrans 250cc

Postby NewKidOnTheBlock » Sun May 18, 2014 2:09 pm

I bought the Mototrans engine complete, and stripped it myself. That’s not to say it is as it left the factory though as there was red-gasket sealant throughout and the bore is 69.5mm suggesting that it’s already been re-bored.

Yes, I had noted that the bolt spacing is different between the two.

From what information I had gathered elsewhere I was under the belief that the scrambler cam should have 8.2mm inlet and 8mm exhaust lift and that the 7.2 I have was likely from a sebring or monza, however I do not know this to be true.

My measure of a ‘fortune’ is perhaps a little vague for your liking, I’m looking to buy my first house this year and so do not want to squander all of my deposit money on the bike, however I am perhaps too impatient to wait years until I build this engine.

The photograph attached to my last post was of the cam which came out of the mototrans engine, with a 25mm base circle and 32mm(ish) peaks.

DewCatTea-Bob
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200-type Camshaft listed on eBay

Postby DewCatTea-Bob » Sun May 18, 2014 2:16 pm

[quote= Jon Pegler ...
" E-bay item 321337317204 is a camshaft that would fit an A series 175 or 200. "

____ These slightly shorter camshafts will fit & work in all 175 thru 450 cyl.heads.
__ Here's an actual link to the eBay-listing... http://www.ebay.com/itm/321337317204?ru ... 26_rdc%3D1
I've included an adjusted-pic with enhanced viewing, as seen below.


Duke-Cheers,
-Bob
You do not have the required permissions to view the files attached to this post.
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob

DewCatTea-Bob
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Joined: Sun Nov 01, 2009 10:53 am
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Re: Tuning a Mototrans 250cc

Postby DewCatTea-Bob » Sun May 18, 2014 4:44 pm

[quote= NewKidOnTheBlock ...
" I bought the Mototrans engine complete, and stripped it myself. "

____ Good,, then it's more likely that the cyl.head you got with it, is original to the rest of the motor.



" Yes, I had noted that the bolt spacing is different between the two. "

____ Have you yet happened to-have noticed the thread concerning another member's endeavor to fit a std.250-head/top-end in place of the Mototrans/200-type parts ?



" From what information I had gathered elsewhere I was under the belief that the scrambler cam should have 8.2mm inlet and 8mm exhaust lift "

____ Have you not-yet read my point that there have been a number of such Scr.camshaft-models, all with the same 'White' color-code ?
The figures you mention seem to be those as once posted by Eldert, who I much-suspect got the "white" camshaft he measured from a non made for USA 450-Scrambler model-version,, as I-myself have never measured a White-cam with quite that much lobe-height ! _ All the w-c.Scrambler-cams I've ever removed from stock 250 & 450 USA.models, measured to be 8.0 & 7.8mm !



" and that the 7.2 I have was likely from a sebring or monza, "

____ The 'Violet' Monza-cam (also stock in the Sebring), has lobe-lift heights consistently between 7.6 & 7.4mm !



" The photograph attached to my last post was of the cam which came out of the mototrans engine, "

____ Interesting ! _ As it's profile doesn't follow the long/well established rule of obvious 'asymmetrical' lobe-ramps of Ducati's own wild-cams (which keep the valve-lift rather high during the overlap-phase) !
I now gather that Mototran's wild timing-figures & low lift-height explain the somewhat rather flat-top looking appearance of the ex.cam-lobe in your picture (which I've posted). _ (Perhaps that's having to do with what Jon had-before referred-to with his use of the word "clever" ?)
__ Anyhow,, now that you know considerably more about your two camshafts, which one are you preferring the most ?
The stock-cam ought-to allow for much increased RPM & power AFTER you open-up the intake-tract ! _ While your mild-cam (which really isn't too mild), would better take advantage of the long-stroke engine-configuration and not really require your intended porting-work quite so much.
At least now you don't really have-to spend your funds on expensive camshaft concerns,, which is too-bad in a way, cuz THAT could've been a much more interesting route to go-down !


Duke-Cheers,
-Bob
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob

NewKidOnTheBlock
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Location: Oxfordshire, UK

Re: Tuning a Mototrans 250cc

Postby NewKidOnTheBlock » Sun May 18, 2014 5:29 pm

I haven't yet seen the thread regarding fitting a ducati head to a mototrans cylinder but I shall take a look!

For your information see the photos on this link, they will probobaly help to answer more questions than I have with words alone: http://imgur.com/a/DTuDB

And yes I had noted your comment about there being various 'white' cams, however perhaps in my naivety I'd assumed them to have the same lift, as I'm learning more and more with these engines it's never safe to assume anything!

To be quite honest I don't know which I would prefer to use, perhaps If I get the head work done that I was intending to then swapping the cam isn't such a huge challenge later on if I find I don't like one.

Does a 37mm exhaust 33mm intake combined with the stock mototrans cam and a 28mm carb sound reasonable? How about my stock conrod? Does anyone have experience running these with more power or more RPM?

DewCatTea-Bob
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Re: Tuning a Mototrans 250cc

Postby DewCatTea-Bob » Sun May 18, 2014 6:31 pm

[quote= NewKidOnTheBlock ...
" I haven't yet seen the thread regarding fitting a ducati head to a mototrans cylinder but I shall take a look! "

____ The fellow in Spain adapted an entire 74mm-bore top-end to a Mototrans-250 bottom-end such as that which you have.
Here's a couple links to his two related threads... viewtopic.php?f=3&t=40&p=169&#p159 & viewtopic.php?f=3&t=1468&p=10426&#p10405
And if those thread-posts interested you, then this link may be of interest as well... viewtopic.php?f=3&t=761&p=5248&hilit=300cc#p5248



" see the photos on this link, they will probobaly help to answer more questions than I have with words alone: "

____ I scrolled-through about 18-pix before my browser froze-up & crashed !
The best lit pic.shots looked as if taken outdoors with your light-source being solely from a rather bright full-Moon, while the rest appeared as if merely lite indoors by Moon-light shown-through an open window. - (Did your home suffer from a power-outage during your picture-taking session last night ? :lol: )
Anyhow,, I'll search for those pix within my temp.internet-files and see what I can do to make their subject-targets more visible.



" I don't know which I would prefer to use,
swapping the cam isn't such a huge challenge later on if I find I don't like one. "

____ Once the in.port is enlarged, the stock/wild-cam will help high-RPM power at the expense of reduced low-end power,, while the White/Scr.cam would provide more responsive take-off/quick-launching fun-type power-delivery (such as 'singles' are most favored for !).



" Does a 37mm exhaust 33mm intake combined with the stock mototrans cam and a 28mm carb sound reasonable? "

____ Except for that you have the valve-positions reversed,, yes, all-that along-with an intake-port appropriately matched to the larger carb, seems fairly-reasonable. _ However with the stock intake-port's dia.size much increased, you ought-to realize that the undesired-effects of such an extra wild-cam at low-RPM, will then become more notably intensified !


Hopeful-Cheers,
DCT-Bob
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob

jezza
Posts: 26
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Re: Tuning a Mototrans 250cc

Postby jezza » Sun May 18, 2014 9:26 pm

Are you aware of Brian Silver, based in Bracknell? He's done a load of work on my engine to bring it from Monza to mach 1 (ish) spec, including having the cam re profiled. He trades as Moto Marianna, does a very good job, and is a luddite so you'll have to phone him. 01344 487920, if he doesn't pick up start talking and he might just magically appear. Otherwise he will call you back.

Hope this helps,

Jeremy

DewCatTea-Bob
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Cam-reprofiling

Postby DewCatTea-Bob » Mon May 19, 2014 12:46 am

[quote= jezza ...
" He's done a load of work on my engine to bring it from Monza to mach 1 (ish) spec, including having the cam re profiled. "

____ So was it really possible to alter your Monza-cam into the specs of a Mach-I/Gray-cam, or just merely approach the wilder specs ?
Sure wish you had a set a pictures of it to examine !
__ I can easily accept that a Monza-cam could possibly be refashioned to match the 'lift' & 'timing' specs of the Mach-I cam.model, but not so sure that it's very-same extents of overlap-profiles could also be identically matched (without building-up the cam-lobes first).
But such a M1.ish-cam should still be fairly impressive anyway !
__ Can you tell us any more about it ?



" Hope this helps, "

____ Hopefully NKOTB will find-out.


Duke-Cheers,
-Bob
PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob

LaceyDucati
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Re: Tuning a Mototrans 250cc

Postby LaceyDucati » Mon May 19, 2014 4:53 pm

As Eldert said Phil Joy is the man for reprofiling cams in the UK. He uses Nickel Stetite welding ( As Megacycle also appears to do).

As far as I know Phil does not have a grey Master, mostly race profiles. The base circle of the doner cam needs to be bigger than the one you are producing, which normally works if you are going from a more "cooking" cam to a "hotter" profile. Finished profiles would be an exact copy to the master. His work is good and he's one of "the good guys", only problem is, being one guy, timescales can be an issue. I'm sure if he charged for what the job should be, he would have less customers and time scales would improve!

Other things to note: You often get stress cracks in cams repaired in this way, but they seldon cause any problems. Sometimes slight distortion in the journals is present, but again never normally cause any real issues.

He does have the green and white profile, but I wouldn't bother as it won't be suitable.

I've already given my advice on this topic in person some time ago.

Regards Nigel


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