Crankshaft problem

[ChangSifon]

HI!! I managed to disassemble the crankshaft aaand find this thingy ...http://postimage.org/image/wbpjbk1gb/
I was using cheap gearbox oil and the bike just died ...The part is one of the bolts used on the crankshaft(the one that the connecting rod is attached to)
Soo the question is , is there anyway to fix it or buy new one from somewhere because I miss my bike ( The bike is RT 125)





Sorry, English is not my first lang

[DAVID THOMPSON]

the crank is probably supplied as a whole unit
can you post a picture with more of the parts included so we can better tell which piece this is in the assembly

too get a new one you will probably have to have a machinist make one or buy a complete crank
dave

[radiograf]

It looks as if this is what we call the big end here in the UK, and that its from a pressed up crank. If so, it should be possible to replace that part, if it is available. A good engineering firm should be able to manufacture one if the part is no longer available. Having said that, a good second hand engine may be a cheaper option.

[djsbriscoe]

Problem is second hand MZ RT125 engines are unobtainium.

Here are two firms from old bike mart (UK)

P Seager Engineering www.seager-engineering.biz (Ipswich,UK)
T & L Engineering www.tandlengineering.co.uk (Elstow,Beds,UK)

HTH,

David

P.S If it was work on your cylinder head that you needed doing I could recommend Serdi UK Ltd in Uxbridge. My bike is running very well after the work they did on the valves and valve seats. Not sure if they do work on crankshafts though.

[radiograf]

Is this the DKW rt125 two stroke, or the MZ four stroke we are dealing with?

[DAVID THOMPSON]

and the year

[ChangSifon]

Is this the DKW rt125 two stroke, or the MZ four stroke we are dealing with?

4-stroke, 2003y

The mechanic is the only one in the country who can disassemble and assemble the crank correctly , and somehow he is my uncle .I tried to find 2-hand engine but the bike is very very rare here :X

[radiograf]

Grahamesmotorcycles.com list the crank at £444 , and there is a 125SM engine on British ebay for £300 (also ) I think your best bet is to get the crank reground and oversize bearing shells fitted.
Just checked, £444 = 1086 Lev, sorry!

[DAVID THOMPSON]

these are rare every where
the state i live in in the usa has almost 2 million people
as far as i can tell i have the only rt 125 4stroke

the best bet is get a machinist to make a new pin
dave

[ChangSifon]

Grahamesmotorcycles.com list the crank at £444 , and there is a 125SM engine on British ebay for £300 (also ) I think your best bet is to get the crank reground and oversize bearing shells fitted.
Just checked, £444 = 1086 Lev, sorry!

For that amount of money I can buy a new bike And I was thinking about bigger bearings, but the mechanic said that I must find new connecting rod with smaller diameter to fit the regrounded bolt/pin.

[radiograf]

A bearing shell is a white metal ring of your standard big end size, which allows you to use a standard con rod. The crank part is ground down to fit inside the bearing shell. You have to remember to drill a hole in the shell and align it with the oilway in the crank, or you'll seize up!

[djsbriscoe]

More photo's please. Or point out the item numbers in these diagrams you are talking about

http://www.grahamsmotorcycles.com/2010% ... linder.htm

http://www.grahamsmotorcycles.com/2010% ... kshaft.htm

Do you have a workshop manual?

Here's a pdf version. Get it while you can.

viewtopic.php?f=4&t=5323&p=27289&hilit=rt125+manual#p27289

David.

[radiograf]

The part pictured is the part of the crank that the con rod rotates upon. It is not pictured in either of the two exploded parts diagrams provided. It would appear that the crank and conrod are only available as a unit.

[ChangSifon]

Sry for not posting guys (had no chance to post) . The part is rdy ! , but still a lot of work on the engine needs to be done. Week or two and the bike would "fly" again . Ill post some pics later

[DAVID THOMPSON]

do not forget the spring and ball bearing on the front top right side that sets oil pressure
dave