raschkadt125 Posted January 21, 2011 Posted January 21, 2011 Hey everyone my name is Greg and am now to this forum, I found a really good deal on a dt175 motor while in the process of gathering a parts list to rebuild my 125. Ican get the 175 for cheaper than I can build my 125 due to missing parts. Is this swap possible and what mods would have to be done. Im up for more power for less money. I have a 1981 (Ibelieve a dt125 e?) no title just off road. I bought it stripped down and does have a mono shock so I know the era not the model(I know it is not the dt125r because of the distictive gas tank. Any info would be greatly appreciated.(seens to be more parts for the 175 too!!! Thanks for looking!!
Moderator Cynic Posted January 21, 2011 Moderator Posted January 21, 2011 Just swap the barrel and piston over with the cylinder head and drop the main jet a couple of sizes, need the frame number to know for sure as some of the carbs have surprisingly varied mains. Thats it, wiring, exhaust everything else is the same. Ignition timing might need the tinyest tweak but again frame number to be certain.
raschkadt125 Posted January 21, 2011 Author Posted January 21, 2011 Thanks for the info I read some where about that, but wasnt sure about the wiring and such. Do they use a common crank and rod then? My crank and rod were rusted togeather, but freed it loose. I would imagine since that they are needle bearings that the crank surface is ruined as well as the rod. I have not split the cased yet to remove the crank so im unsure as how the rod seperates from the crank( is there a pin to press out if so that would give me a smooth surface by pressing in a new pin with new rod a bearrings?). And what about the crank end bearrings do they press onto crank or, ride on the crank,( if they ride on the crank I would have to replace that too) what would be a good year 175 motor to either use or take parts from? Thank you for all the information and helping a newbie to the forum!!
Moderator Cynic Posted January 21, 2011 Moderator Posted January 21, 2011 Thanks for the info I read some where about that, but wasnt sure about the wiring and such. Do they use a common crank and rod then? My crank and rod were rusted togeather, but freed it loose. I would imagine since that they are needle bearings that the crank surface is ruined as well as the rod. I have not split the cased yet to remove the crank so im unsure as how the rod seperates from the crank( is there a pin to press out if so that would give me a smooth surface by pressing in a new pin with new rod a bearrings?). And what about the crank end bearrings do they press onto crank or, ride on the crank,( if they ride on the crank I would have to replace that too) what would be a good year 175 motor to either use or take parts from? Thank you for all the information and helping a newbie to the forum!! If the crank is rusted then chuck it out. Another motor is by far the easiest option. The actual cranks are pretty bomb proof. The crank bearings ideally want a puller to get them off but none of it is that hard for basic mechanics. If the 175 motor you have is good then bolt it in, don't faf about with the 125.
raschkadt125 Posted January 21, 2011 Author Posted January 21, 2011 thanx for the info- so the crank bearrings dont ride on crank but rather press on-good, now how does the rod connect to crank, (does the crank sepperate or do you press out a pin, insert new rod and press in a new pin) The 175 I found is on ebay, doesnt run but cylinder is good and so is piston, so i was just thinking re ring it. The bike I have is is strpped but in real good shape not rusted or dented. I want to seperate the motor clean everyting and paint it, as long as im this far into it, I might as well do it right. (all new gaskets and seals bearring ect.) I think it would be easier using parts from the 175 since I plan on stipping motor completely( dont trust jsut installing the 175 and hoping it works out.) Are there any concers I should be aware of when splitting the cases, special tools?, or stubborn bolts? agin thank you for the info cant wait to have another 2stroke running. ect. what would be the advantage of having a weisco piston over stock (are they diffent cc's or just lighter, stronger?
Moderator Cynic Posted January 21, 2011 Moderator Posted January 21, 2011 thanx for the info- so the crank bearrings dont ride on crank but rather press on-good, now how does the rod connect to crank, (does the crank sepperate or do you press out a pin, insert new rod and press in a new pin) The 175 I found is on ebay, doesnt run but cylinder is good and so is piston, so i was just thinking re ring it. The bike I have is is strpped but in real good shape not rusted or dented. I want to seperate the motor clean everyting and paint it, as long as im this far into it, I might as well do it right. (all new gaskets and seals bearring ect.) I think it would be easier using parts from the 175 since I plan on stipping motor completely( dont trust jsut installing the 175 and hoping it works out.) Are there any concers I should be aware of when splitting the cases, special tools?, or stubborn bolts? agin thank you for the info cant wait to have another 2stroke running. ect. what would be the advantage of having a weisco piston over stock (are they diffent cc's or just lighter, stronger? I say again if the crank is duff or big end, bin it. It IS NOT a diy job to set a crank up and its not woth the expence, esp on a dirt only bike. Just fix up the 175 and chuck the 125, keep the cases if you want for the numbers but if the crank has rusted ITS B@@@ocked. All you need to strip the motor is a manual like Haynes, or clymer, a flywheel puller (about a tenner from e-bay) a heat gun and patience. The engine bearings and gaskets can all be bought for around 80quid.
raschkadt125 Posted January 21, 2011 Author Posted January 21, 2011 Good to know on the crank I didn't know if they were rebuildable or not. I guess I will see whats up with the 175 and if not complete I can use parts off of the 125. thank you for advice!!
raschkadt125 Posted January 21, 2011 Author Posted January 21, 2011 If you had a choce of rebuilding the 125 (new gaskets, seals, crank, rod, piston) or getting a used 175 and doing a build to that, or is there a larger motor than the 175 that still bolts to frame, which would be your plan of attack? I want the most power i can get but not have to make a custom mounts and such,( from my digging around it seems to leading twards the 175 if so does anyone have one for sale?
Moderator Cynic Posted January 22, 2011 Moderator Posted January 22, 2011 If you had a choce of rebuilding the 125 (new gaskets, seals, crank, rod, piston) or getting a used 175 and doing a build to that, or is there a larger motor than the 175 that still bolts to frame, which would be your plan of attack? I want the most power i can get but not have to make a custom mounts and such,( from my digging around it seems to leading twards the 175 if so does anyone have one for sale? Actually if all you want is horspower at the cost of all else then....... I believe (I HAVE NOT CONFIRMED THISbut anything will fit anything if you really want it) the TZR 125 motor will go in without a lot of work. Adapt the exhaust and fit a rad and a coolant bottle your looking at 20+ hp with the pv pegged wide open. Realistically the 175 is the better motor it has good torque as the 125 is all revs. Sports exhausts are readily available from Big One and parts are in the main still available from many pattern and Yamaha dealers. There really is very little difference between the engines, i think it was always meant to be a 175 as that was a very common capacity in the 70's and they stuck a 125 on top to complete the range. It is also an incredibly stron motor that will run when many others wont. Mine was still running with 2 blown crank seals and bearings, a cracked inlet rubber and slipped ignition that was far enough out to damage the piston crown. Still got me to work, admittadly 45mph was about all she had wheras now 60+ is comfortably achievable it just shows what these engines can take. 125/175 175 no question.
raschkadt125 Posted January 24, 2011 Author Posted January 24, 2011 I looked up the TZR 125 on ebay to see the availability of parts and was shocked to only see 4 pages. Seems to be way more parts out there to keep either the DT 125/175 running down the road. The DT 175 seems to be my best option. I'm going to keep my eyes out for open for a decent motor with a solid lower end, and a rebuildable top end.( I think a coupe gaskets and some rings would be a good way of finishing a good inspection). I'd rather not have to seperate the cases if I dont have too. The cost of parts to make my stock lower end up to par would be probably more than buying a solid 175, and just freshin up the motor and call it good. 1. Is there enough clearance to shave material off the head to bump compression. 2. Is there any port and polishing that could be done, (I have done it on four stoke motors but not sure on the effects it would have on a two stroke.) 3. Is the a patronics system or simular, that replaces the points with a magnetic pickup sensor. 4. If I want to premix the gas and oil do I just remove the oil pump and plate it off? I appreciate all the help I'm getting, I'll keep you posted and hopefully get some pics up.
Moderator Cynic Posted January 24, 2011 Moderator Posted January 24, 2011 Oh you have one of the early 125's. Get yourself a dt175 mx (80 -on) cdi and stator plate and flywheel and bolt it on connect them up, all the connections are there pretty much and you have electronic ignition . As far as tuning goes the engines don't like it TBH they get all nasty with horrid carbration. A sports exhaust and filter is good enough with those brakes. Mine will touch 70 on a good day and lift the front wheel if you are ham fisted with the throttle. Which side is the oil tank on yours, this is going to sound stupid but bikes with the oil tank on the left of the bike are faster due to a different filter/airbox arrangement.
raschkadt125 Posted January 24, 2011 Author Posted January 24, 2011 Is there a good year and a bad year for the 175. I located a 1974, 175 motor and plan on buying in a few days, should I be looking for a certain year? The engines complete minus the carb. Sounds like a solid motor ( its clean, cosmetically good shape), and owner stated that it had good compression when pulled. Just a question on the 175, was the dt the later mono shock, and the mx is the earlier dual shock. Thanx for the help![b]
Moderator Cynic Posted January 24, 2011 Moderator Posted January 24, 2011 Is there a good year and a bad year for the 175. I located a 1974, 175 motor and plan on buying in a few days, should I be looking for a certain year? The engines complete minus the carb. Sounds like a solid motor ( its clean, cosmetically good shape), and owner stated that it had good compression when pulled. Just a question on the 175, was the dt the later mono shock, and the mx is the earlier dual shock. Thanx for the help![b] No, and there were 2 175 motors in 1974 the CT series and the AT series carb/reed options varied and the number of transfer poorts can be different. The DT prefix (Dirt Trail) prefix appeared in the early seventies on the 125/175 the MX bit indicates the later mono shock. You are looking at a twinshock motor that should fit ok but i can't gaurantee the cdi ig will fit for eg, and its won't go as well. You really want to be looking for an MX motor from 79 to 83.
raschkadt125 Posted January 24, 2011 Author Posted January 24, 2011 The motor im looking at says ID# 443-013867. What would be the advantage having the mx over the dt motor. From what ive researched many refer to the mx's having both monoshock and dual shock. I wasnt finding much out there for mx motors so, if there isnt much power difference im going to go with the dt175, might not be as good as the mx but still is better than the 125 I currently have with is ok with me. I still havn't been out by my bike lately to get any numbers off of it.
Moderator Airhead Posted January 24, 2011 Moderator Posted January 24, 2011 Its all abit confusing, our MX's were your (American) DT175E, F, G The prefix is 2A7 They were the monoshock bikes with 6 speed transmission However from what I understand the American MX's were without some street running gear werent they, lights, horn and the like (not 100% on that though) The prefix 443 is DT175A, B. As Cynic said it is an earlier bike, (twinshock) 5 speed. The engine will fit I think and for a field bike would be fine, I think that there is a slight difference in the chain run (5mm more outward on the monoshocks) but that shouldnt matter really on a field bike. However the electrics are different and the early bike runs with points.
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