what 125 engine????

[Paulwhite]

hi all as some of you know im building a xvs bobber and soon il be needing an engine. but im not sure what to get, 4 stroke or 2 stroke? im in need of a 125cc engine but im wanting to be able to hit at least 70mph which means more bhp but at the same time i need it to be reliable.

iv had my eye on a pitbike engine for some time now but its going to cost me about £1000 to be able to bolt it in and go, to be honest its not really suited to what im looking for but it is brand new and the parts are cheep plus its easily tunable!

so my question is what engine would you recommend? note that il need everything to make it work like loom, reg/rect ect ect. and my budget cant go over £1000.

cheers . Paul .

[Cynic]

There is a DT125MX motor under my bench, needs a rebuild but that can be done comprehensively for under 250. As for a loom to make it run. 1 wire Aircooled to boot so no plumbing issues. An exhaust would sting you another 80 odd quid for a new one but if you can get a stocker off ebay which are not all that rare you could cut it about to suit the bobber.

Most importantly it is a 125 that can, (although you'd be a very naughty boy) make into a 175 in about 20minutes if your handy with the spanners. Also the details for the 'big bore' are in the std manual ie std dt175.

With the right gearing i can see that hitting 70 in a bobber readily enough, they book at around 17hp

[Paulwhite]

well the pitbike engine im looking at is a oil cooled 125cc 15bhp tunable to 17bhp. but it uses a 140cc bottom end so i was going to get a 140cc barrel/piston and stage 3 tuned head with matching carb to get it to 19+ bhp , sounds good if not a little naughty but the engines are notorious for being high maintenance and unreliable.

nice offer though defiantly something to think about im very tempted but im just comparing the engine iv found to others, to compare the pro's and cons and try and make my mind whilst i raise the funds, i wouldnt mind getting a 2 stroke for the power but im not sure how reliable they are.

im looking for a good mix of power and reliability but it has to pass as a 125 learner legal till i can save up for my direct access, i mean im 23 and have 7 years riding experience (not allot yet but more than some) and i dont see the need to get a massively big engined bike. i just want to be able to overtake a bus or lorry more safely plus im getting a little tired of struggling to get over 40mph up a hill on a dual carriageway. im also thinking of selling it and i think id get more for it if it had a better engine but at the same time i need to be able to ride it.

[Cynic]

im looking for a good mix of power and reliability but it has to pass as a 125 learner legal till i can save up for my direct access, i mean im 23 and have 7 years riding experience (not allot yet but more than some) and i dont see the need to get a massively big engined bike. i just want to be able to overtake a bus or lorry more safely plus im getting a little tired of struggling to get over 40mph up a hill on a dual carriageway. im also thinking of selling it and i think id get more for it if it had a better engine but at the same time i need to be able to ride it.

Well speaking from experience the engines are bloody near bomb proof, they are a 175 engine with a 125 top end. No visual difference bar a 6 bolt cyl head and obviously 175 stamped on the bottom of the barrel but that can be tweaked. The same (or very very similar crank set) is used in the DT230 Laval which is knocking 30+hp, although there is not a lot left for tuning at that stage.

I'm sure OG will back me up amongst others that one of these lumps screwed together with some care is a solid gold bet. Not state of the art but strong, reasonably pretty, good parts and easy to fix. Doesent rev very high (the 175 tops at around 8000) but has the torque to get round that.

Like i say its there, it will all as likely still be there at christmas.

[Paulwhite]

nice one well its beaten the pitbike engine for reliability and power lol (not to mention price!) the 8000 rpm sounds a little low compared to the 1400 the pitbike engine was boasting but as iv said im looking for power with reliability so the dt125 engine is looking the better option! sow how much were you looking to sell it for? and what parts would come with it?

[Cynic]

nice one well its beaten the pitbike engine for reliability and power lol (not to mention price!) the 8000 rpm sounds a little low compared to the 1400 the pitbike engine was boasting but as iv said im looking for power with reliability so the dt125 engine is looking the better option! sow how much were you looking to sell it for? and what parts would come with it?

PM sent.

[Paulwhite]

hmmm im a little unsure its a good engine dont get me wrong but it needs work, and it can only get up to about 17bhp, where as the pitbike engine comes in at 15bhp tunable to over 19bhp, plus its new verses 2nd hand, and another note is parts availability and cost, the dt engine parts are more expensive and i cant seem to find anywhere with a good parts list (probably looking in all the wrong places) and iv had a look on the ty trials website. here is a link to the pitbike engine iv found take a look and tell me what you think. PITBIKE ENGINE

[dan28]

i have an xvs chopper too

does it have to be a yamaha engine

what about a cagiva 125 engine i m told they have a 7 speed box an do 90 mph as standard not sure how true that is though

[Paulwhite]

yeah that is true the cagiva mito 125 engines are about 37 to 40 bhp and can do over 100mph BUT and this is a big but! they are like a 16 year old on a nicked apprilia rs 125!! (they braek down and need re-building every 2 min!) but yeah they are a mint engine if you want to keep re-building the thing, but i dont want to have to strip it down every 2 min!

and no it dont have to be a yamaha engine. im looking at the pitbike engine as there cheep as chips and as long as you look after them they can last a while! say for instance the bottom end goes.....it would only cost 150 quid to buy a brand new one! most of the time its 150 quid just for the gasket set! plus the power is quite good for a 4 stroke!

and nice bike ( well from what i can see) any chance of some pics? i havent seen any modded dragstars (and i have looked for ages!) if you wanted you could have a look at what im trying to do... just search the forum for "xvs 125 bobber update" and you should find it.

soz if there are any spelling mistakes iv hijacked me m8s comp and he hasnt got the spell check lol (plus spelling isnt something im good at lol)

cheers. Paul.

[dan28]

yeah that is true the cagiva mito 125 engines are about 37 to 40 bhp and can do over 100mph BUT and this is a big but! they are like a 16 year old on a nicked apprilia rs 125!! (they braek down and need re-building every 2 min!) but yeah they are a mint engine if you want to keep re-building the thing, but i dont want to have to strip it down every 2 min!

and no it dont have to be a yamaha engine. im looking at the pitbike engine as there cheep as chips and as long as you look after them they can last a while! say for instance the bottom end goes.....it would only cost 150 quid to buy a brand new one! most of the time its 150 quid just for the gasket set! plus the power is quite good for a 4 stroke!

and nice bike ( well from what i can see) any chance of some pics? i havent seen any modded dragstars (and i have looked for ages!) if you wanted you could have a look at what im trying to do... just search the forum for "xvs 125 bobber update" and you should find it.

soz if there are any spelling mistakes iv hijacked me m8s comp and he hasnt got the spell check lol (plus spelling isnt something im good at lol)

cheers. Paul.

ah i see

there are some pics of mine search my posts an look in the poor running thread

i ve already seen your bobber project ( ive posted a reply on it) it looks good but there doesnt seem to be much clearence between the mudguard an tyre

the pit bike engines arent designed to be rode all day they how durable are they like cr 125 s for example if you ride them for long periiods you are forever changing piston an rings

[Paulwhite]

yeah i havent attached the mudguard yet its just resting on the tire lol, i might re-think the rear fender though, iv sen a nice idea in this months B,S,H magazine, where the seat is also the fender, iv also decided not to use a springer seat (now makes the ride hight lower) as iv said im going for a "light as possible" frame without compromising on safety, so instead of having a fender and a seat im gonna combine the two, should save a little on weight

i hear what your saying about the pitbike engine there not all that reliable but if you weigh up reliability verses cost and power then there a very good engine, but thats the point of this thread! im still undecided about the pitbike engine but unless someone can come up with a good argument why another engine would be better, then its the one im going to get

[KirriePete]

A grand for a glorified C90 engine? I haven't paid that much for a whole bloody bike, let alone an engine!

If it were me I'd go down the DT125/175 route if only for the look of the thing - you do know that the pitbike engine will hang down around your ankles and leave a huuuuuuuge gap up to the tank, don't you? As for reliability, as others have mentioned, these hopped-up engines are designed for short bursts of speed, not prolonged road use .... it may prove to be as reliable as the Cagiva engine mentioned further up this thread.

Or .... blasphemy time .... get your hands on a Suzuki GP125 mill, the last of the great aircooled stinkwheels, did a realistic 80 out of the crate and could survive the hamfisted attentions of most teenage bodge artists of the time .... or a Kawa KH125 - they made them for bloody years so there's thousands of the wee buggers laying about and they're tough as old boots .... or a Yam RS/RXS 125 .... All of these stinkwheel singles were the sort of motors the Japs could churn out with their eyes shut, simple, rugged, reliable, easy to work on and tune, vast amounts of spares lying around, oh yes, they look good as well.

Go on, you know you want to!

[dan28]

if you do change the mudguard design send me a pm if the old fender is up for sale

[Paulwhite]

A grand for a glorified C90 engine? I haven't paid that much for a whole bloody bike, let alone an engine!

If it were me I'd go down the DT125/175 route if only for the look of the thing - you do know that the pitbike engine will hang down around your ankles and leave a huuuuuuuge gap up to the tank, don't you? As for reliability, as others have mentioned, these hopped-up engines are designed for short bursts of speed, not prolonged road use .... it may prove to be as reliable as the Cagiva engine mentioned further up this thread.

Or .... blasphemy time .... get your hands on a Suzuki GP125 mill, the last of the great aircooled stinkwheels, did a realistic 80 out of the crate and could survive the hamfisted attentions of most teenage bodge artists of the time .... or a Kawa KH125 - they made them for bloody years so there's thousands of the wee buggers laying about and they're tough as old boots .... or a Yam RS/RXS 125 .... All of these stinkwheel singles were the sort of motors the Japs could churn out with their eyes shut, simple, rugged, reliable, easy to work on and tune, vast amounts of spares lying around, oh yes, they look good as well.

Go on, you know you want to!

cheers lol.yeah its not a grand in total just something like £800 for the 125 engine (brand new and tuned to 15 bhp with a 140cc bottom end) and everything i need to convert it to a 140cc 19bhp race tuned engine, plus custom exhaust's, stator and wiering loom.

i am aware that the engine is going to be small but i would say it would be lighter. plus will leve room for a custom air filter cover.......or even a turbo..... im gonna go do some research on them engines to see how good they are in terms of reliability, power, and parts availability / cost and il get back to you, cheers for the info!

oh and dan28 il most likely re-make the rear fender so once thats done il pm u