swooshdave Posted January 29, 2008 Report Share Posted January 29, 2008 I gentleman over on TeamBultaco (Yahoo Group) posted these pictures. With his permission I'm reposting them here. Does anyone know the history behind this bike? Were they ever produced? Quote Link to comment Share on other sites More sharing options...
woody Posted January 29, 2008 Report Share Posted January 29, 2008 It's very well done, there is an article on it somewhere on the net but can't remember where now. However, someone has done an even better one than that. On Todotrial somewhere, there's a picture of a blue Bult converted to 4 stroke using the Bult bottom end - you have to look twice to realise the top end is not what it should be. Quote Link to comment Share on other sites More sharing options...
stu Posted January 29, 2008 Report Share Posted January 29, 2008 Has been done before to Montesa by PORTUS a well known preparator around Barcelona, he used a Sandglass 4 stoke head mounted on 348 Montesa, going back around 20 years, was a very nice thing. Quote Link to comment Share on other sites More sharing options...
tlrs Posted January 29, 2008 Report Share Posted January 29, 2008 (edited) portus: a 4T montesa conversion Edited January 29, 2008 by tlrs Quote Link to comment Share on other sites More sharing options...
swooshdave Posted January 29, 2008 Author Report Share Posted January 29, 2008 How to they drive the valves on a two-stroke lower end? Quote Link to comment Share on other sites More sharing options...
tlrs Posted January 29, 2008 Report Share Posted January 29, 2008 bleutooth ? Quote Link to comment Share on other sites More sharing options...
swooshdave Posted January 29, 2008 Author Report Share Posted January 29, 2008 bleutooth ? Close. I found a Spanish trials forum that mentioned (in translated English) a toothed belt and showed the same picture as above. No picture of the right side. I assume that it was driven from the crank end. I believe the Montesas were gear driven primaries so no chain (like a Bultaco) to get in the way. The bike is now apparently in a Spanish museum. The Bassella Motorcycle Museum Quote Link to comment Share on other sites More sharing options...
toofasttim Posted January 30, 2008 Report Share Posted January 30, 2008 Dave, read the pamphlet carefully. It's a homebuilt. A VERY professional job but still a homebuilt. Quote Link to comment Share on other sites More sharing options...
peterb Posted January 30, 2008 Report Share Posted January 30, 2008 I've never seen the Portus Montesa before, nor even heard of the Rotax Bultaco - which does look a little large in the stretched out frame. Excellent postings. I saw the 4T Bultaco aslo in Todotrial, it looked like a Honda TLR250 top end on a Bultaco M199 bottom end, got me thinking for my next project! I always fancied building up a 4T with a spare Bult bottom end, I wonder where the oil pump would be driven off and how to get the oil onto the camshaft. Bye, PeterB. Quote Link to comment Share on other sites More sharing options...
spud plark Posted January 30, 2008 Report Share Posted January 30, 2008 A one off project from Manel Blancafort From: http://todotrial.mforos.com/65594/4821907-...ferentes/?pag=2 Quote Link to comment Share on other sites More sharing options...
swooshdave Posted January 30, 2008 Author Report Share Posted January 30, 2008 Dave, read the pamphlet carefully. It's a homebuilt. A VERY professional job but still a homebuilt. Yes, I'm sure the first one was homebuilt. I was just wondering if any more were made and why they weren't through the trouble of making a brochure. Quote Link to comment Share on other sites More sharing options...
toofasttim Posted January 30, 2008 Report Share Posted January 30, 2008 To finish off the job and to fool poor saps like us? The brochure is photoshopped. Look carefully at the Bultaco logo on the first page. Quote Link to comment Share on other sites More sharing options...
peterb Posted January 30, 2008 Report Share Posted January 30, 2008 Hi spud plark, Thanks for posting the photos and the Bultaco link. I had a look for a photo of the mag side of the 4T Bult but nothing there, wanted to see how the drive was accommodated for the camshaft. I'll try the guy who posted the original info. Bye, PeterB. Quote Link to comment Share on other sites More sharing options...
dabdab Posted January 30, 2008 Report Share Posted January 30, 2008 Judging by the photos only, the insertion of a full 4 stoke motor with OHV in any conventional trials frame still,even with the Montesa & Sherco on the market today, has the problem of the height of the motor. The ground clearance on the Bultaco picture looked to be a third LESS. But good news is to hand. Has anyone seen the GasGas 4 stroke protype - it uses a SIDE VALVE ( remember them Big John ) to reduce the height issue Quote Link to comment Share on other sites More sharing options...
swooshdave Posted January 30, 2008 Author Report Share Posted January 30, 2008 To finish off the job and to fool poor saps like us?The brochure is photoshopped. Look carefully at the Bultaco logo on the first page. My first impression too. Except that if they were good enough to fake the stamped address on the back they would have been able to make a decent brochure (cleaned up the Bultaco logo, etc.) I'm more along the lines that someone mocked up a quick brochure in the hopes of perhaps moving this into "production". Quote Link to comment Share on other sites More sharing options...
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