rusty nuts Posted August 27, 2018 Report Share Posted August 27, 2018 hi what's involved in turning this into a usable 250 machine . is it head .barrel n piston or is stroke different too . it's guttless and I'm 16 stone you get the picture. Quote Link to comment Share on other sites More sharing options...
naichuff Posted August 27, 2018 Report Share Posted August 27, 2018 Nice bike It would be a pity to spoil it The 175 motor and 250 motors look the same but have suttle difference In the ignition fly wheel is lighter Crank balance and gearing I bought one new and still have it The carb may also not be the same Mine is as it left the factory Have not had the head off yet and runs better than my pal's 250 Yes have to rev it more I also use a larger twin air filter as when new found dirt behind the one behind that panel Maybe mine breaths better! Quote Link to comment Share on other sites More sharing options...
rusty nuts Posted August 27, 2018 Author Report Share Posted August 27, 2018 thanks for that review might be worth a tune up before I take it apart then it's ever going to be a ty 175 pedigree though I wouldent think Quote Link to comment Share on other sites More sharing options...
section swept Posted August 27, 2018 Report Share Posted August 27, 2018 Nice bike, what’s going on with the gear lever? How about putting a 250 engine or maybe a 325/350 engine in, you then have options. Cost may be off putting. I’m not certain but I think the engine mounts may be the same. Maybe careful setting up of the 175 engine and possibly a heavier drive side flywheel might give you some extra urge out of the motor. Reed valve conversion may also release a few bhp more.? 1 Quote Link to comment Share on other sites More sharing options...
naichuff Posted August 27, 2018 Report Share Posted August 27, 2018 They are not in the same pedigree as the TY 175 The heavy fly wheel do not fit the drive side (the seal carrier stops this) but and it will not pick up as quickly A 250 /325 motor may fit but I am not sure as the frame is different on the front down tube It curves just behind the head stock Quote Link to comment Share on other sites More sharing options...
section swept Posted August 27, 2018 Report Share Posted August 27, 2018 That’s it then, buy my 250 Sherpa! Problem solved. Quote Link to comment Share on other sites More sharing options...
naichuff Posted August 27, 2018 Report Share Posted August 27, 2018 I would another garage this one is full Quote Link to comment Share on other sites More sharing options...
woody Posted August 27, 2018 Report Share Posted August 27, 2018 The 175 uses the same frame as the 250cc (actually 238cc) model 190 Sherpa. The 250 frame from '76 to '78 had the bend at the top of the downtube. The motor is a 250 with cylinder sleeved down to 174cc. This capacity was basically done for rental companies in holiday resorts as the maximum capacity that could be ridden without a licence was 175. I think most of the 175 bikes were for the rental market with dual seats (which may explain the longer rear frame loop than a M190) but some were made as 175 Sherpa T. Don't know about them having a different crank assembly or lighter flywheel but converting to 250 is a top end swap or boring back to 250 (not sure if the head would need modifying for the bigger bore, I've never had one apart so don't know if the 175 has a different combustion chamber) If you need more info speak to Dave Renham at In Motion The 175 uses a 25mm carb whereas the 250 had a 27mm. The 250 would run fine on a 25mm as the early 325 engines used a 25mm carb. The 175 had a higher 1st gear than the other bikes but the rest were the same as the 250/325. 3 1 Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted August 28, 2018 Report Share Posted August 28, 2018 20 hours ago, woody said: The 175 uses the same frame as the 250cc (actually 238cc) model 190 Sherpa. The 250 frame from '76 to '78 had the bend at the top of the downtube. The motor is a 250 with cylinder sleeved down to 174cc. This capacity was basically done for rental companies in holiday resorts as the maximum capacity that could be ridden without a licence was 175. I think most of the 175 bikes were for the rental market with dual seats (which may explain the longer rear frame loop than a M190) but some were made as 175 Sherpa T. Don't know about them having a different crank assembly or lighter flywheel but converting to 250 is a top end swap or boring back to 250 (not sure if the head would need modifying for the bigger bore, I've never had one apart so don't know if the 175 has a different combustion chamber) If you need more info speak to Dave Renham at In Motion The 175 uses a 25mm carb whereas the 250 had a 27mm. The 250 would run fine on a 25mm as the early 325 engines used a 25mm carb. The 175 had a higher 1st gear than the other bikes but the rest were the same as the 250/325. is it just the 125 frame thats smaller @woody? 1 Quote Link to comment Share on other sites More sharing options...
woody Posted August 28, 2018 Report Share Posted August 28, 2018 125 frame probably isn't any smaller or much lighter as the 125 motor still uses full size crankcases. Apart from the twin downtubes, the rest of it looks like a 250 frame from '76 to '78 which used the shorter forks. It even has the bend at the top of the downtubes. I think the only reason the 125 appears to be a smaller bike is the wheels are 20/17 so it sits a bit lower, there is only about an inch or so difference in height between 125 and bigger bikes. The 125 frame was supposedly a prototype for the 250/325 bikes but discarded in favour of continuing with the single downtube (not sure how that would have worked with the side exhaust port unless they were developing a new cylinder) Overall it was prbably a bit lighter but much of that may have come from the smaller top end and possibly a smaller crank assembly A friend of mine had a new 125 and it was truly gutless Quote Link to comment Share on other sites More sharing options...
model80 Posted August 28, 2018 Report Share Posted August 28, 2018 (edited) The last generation of the road going Bultaco Streaker 80cc & 125cc had a centrally located exhaust port. I believe that these formed the basis of the prototype motor which saw the light of day in the Pursang Mk15. This would have gone to be used in the follow on to the 199B Sherpa. This model would have been radically different to preceeding Sherpa's as the drive sprocket was located significantly closer to the swinging arm pivot. Sadly we can only guess at it's potential. Edited August 28, 2018 by model80 Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted August 29, 2018 Report Share Posted August 29, 2018 we put a 125 frame next to a 325 and its smaller and lighter Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.