TZR125 4DL.. my rebuild / guide thingy

[Timmeh]

Hi chaps

I thought that I would spend some time doing a how-to as I've been on this site for ages and not really contributed much to Show'n'Tell so here we go. Very little useful information exists for the 4DLs, having never been offically imported into the UK. Sevice manuals are limited to parts fiches and the user manual which is sketchy and misleading at best. The closest manual for the engine is the DT125 of which the engine bears a passing resemblance, however 4DL engines are license-built by Moto Minarelli and are very different to their jap counterparts.

Hopefully this will be of some info to some. I have made the assumption that, as a 125, most people who ride this bike are learners with little or no experience of maintaining bikes, so it's written that way (apologies to the experts out there).

There are many different ways to drop a lump but essentially they are just two things. 1... getting cables and bits off the bike in some form of logical order and 2... lowering the engine to the floor in a safe, controlled and careful manner.

So, to that end; Make sure the bike is on a study, flat surface; make sure the sidestand is fully down; the ignition, fuel tap and choke are set to OFF. Obviously no smoking or drugtaking is advised whilst working on engine components. It's also good practice to put bolts back into their holes for safekeeping when you take things off. You don't want a bike in bits and a random collection of bolts in a box with no idea what goes where.

As I tend to work on my bikes with little or no help, this is a method for doing all the work yourself. A fair amount of confidence is required. If in doubt, always have someone to help you

So I'll start at the beginning. I assume some basic knowledge of the bike and we'll start with the plastics, seat, tank and airbox already off as that should be obvious.

When referring to locations, assume you are sitting on the bike (so right is your right)

Carburettor

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Fig 1. Basic layout of bike, showing top of carb, induction box, cable junction (centre), YPVS controller (top), servo unit (bottom), wiring connectors (top right). Remember this bike is Italian so the wiring will be a mess. The newer red cabling and the little square box on bottom left is the ballast and wiring for the HID I have on this bike. The cylinder head is just visible with the top water hose poking out.




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Fig 2. Drain the coolant by removing the jubilee clip from the water pump, located bottom right of the engine. Also undo the radiator filler cap to speed up the process.




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Fig 3. Remove the top hose from the radiator. Some more water may come out.




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Fig 4. Details of the carb showing choke circuit, accelerator pump screw, fuel inlet pipe and throttle cable. It is easier to remove the carb after the engine is off the bike.




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Fig 5. Mark a line on the accelerator pump. Slowly wind it in counting the number of revolutions till it stops. Don't force it. Make a note of the count and then unwind all the way until the needle comes out from the carb body (it will come out a long way before the needle is visible.)




https://imageshack.us/a/img19/7805/5choke.jpg
Fig 6. Here we can see the accelerator pump needle out of the carb. Undo the little flat-head screw and withdraw the screw with the choke circuit. There should be a plastic gasket there as well. Beware that the choke plunger is spring-loaded and may be under tension.




https://imageshack.us/a/img41/428/6chokebits.jpg
Fig 7. Release the choke plunger and spring by compressing the spring until you can slide the plunger off the cable. Put in a safe place. The screw is not in this picture but you should keep it all together.




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Fig 8. Remove the fuel pipe off the inlet by removing it. Most likely some petrol will leak out. The mixture screw can be seen just next to it.




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Fig 9. Unscrew the top of the carb and carefully withdraw the slide and needle.




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Fig 10. The slide and needle assembly. Note the orientation, the gold dot goes towards the engine end of the carb.




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Fig 11. Push the spring out of the way, then use a set of needlenose pliers to undo the retaining nut on the slide. The slide and needle will come away, note the spring is under tension and will try to make a break for it. Remove the locknut by sliding it over the end of the cable.




https://imageshack.us/a/img836/7397/11slidebits.jpg
Fig 12. The throttle slide parts. Move them to a safe place, a damaged needle or slide will be nigh-on-impossible to replace without buying a whole new carb.


Engine cables


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Fig 13. Unbolt and remove the engine earth strap, this is located on the RHS of the engine next to the oil filler cap. There is a spring washer underneath. Don't lose it.




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Fig 14. Locate the starter relay which sits to the rear left of the bike by the undertray.




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Fig 15. Peel back the insulator to reveal two gold nuts and the cables. Grip the lower nut with some pliers and undo the top nut to release the starter cable. WARNING: Do not apply pressure to the body of the relay.




https://imageshack.us/a/img842/9656/30startercab.jpg
Fig 16. Locate the wiring loom connector blocks which are at the front right of the frame. There will be some cable ties holding the thing together. Trace the cables that lead from the generator on the LHS of the engine and disconnect them. There is one 4-way block and 2 two-way connectors to deal with.




https://imageshack.us/a/img819/7392/31servocab.jpg
Fig 17. Locate the cable that leads from the servo control unit (big black box on front right of frame) to the servo unit, and disconnect the white connector. Some bikes also have a single cable with an insulated bullet in the middle, which will also need to be disconnected.




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Fig 18. Pull the cables out through the frame down by the side of the engine. Also can be seen is the breather pipe which runs down the RHS of the engine.



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Fig 19. There is little freeplay in the choke cable so removal from the lever end is difficult. Undo the 13mm nut which holds the retaining clip in place. Afterwards replace the nut and tighten up again so it won't come off, as this is also one of the barrel nuts. This is located on the rear right of the cylinder just in front of the induction box.




https://imageshack.us/a/img14/663/14clutch2.jpg
Fig 20. With the clip removed, use a set of needlenose pliers to remove the cable from the clutch arm. It is a little fiddly but will come out.



Sprockets, Chain and Gear linkage


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Fig 21. Time to remove the chainguard by removing the two allen bolts. The top one is far shorter than the bottom one. After removal put the bolts back in.




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Fig 22. The front sprocket. It's always easier to take it off with the engine in the frame.




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Fig 23. Unstake the retaining washer by pushing the tabs flat with a suitable tool. Be careful not to push the bike off the stand, grip the frame with your other hand if need be.




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Fig 24. Use 27mm socket with a long bar extension to take off the sprocket nut. Sit on the bike, apply rear brake and pull the bar towards you. Use progressive force and take care to turn it straight and not at an angle.




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Fig 25. Withdraw the sprocket and remove. Pull the slack chain through the frame so it is clear of the engine.




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Fig 26. To remove the gear linkage, first remove the silver bolt on the selector arm as seen to the right of the sprocket in Fig 21. If there isn't enough play in the linkages to slide it fully off (as was the case with mine), use a set of circlip pliers to remove the whole gear change lever.




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Fig 27. The removed gear lever as it should come off the bike.



Exhaust System


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Fig 28 It's time to get the exhaust off the bike. Firstly undo and remove the two 13mm bolts securing the collar to the engine.




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Fig 29. With the collar off, replace the nuts and washers for safe-keeping.




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Fig 30. To gain access to the mounting bolt, removal of the left footrest is required. Use an allen key or similar to undo the two bolts.




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Fig 31. With the hanger removed push it up and out of the way.




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Fig32. Undo and remove the exhaust bolt, supporting the zorst as you remove it. The system should fall away from the bike.




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Fig 33. Exhaust system off bike. The can should slide through the rear strap and can then be moved away.




YPVS


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Fig 34. Unbolt the left-hand radiator bracket. The front of the servo actuator can be seen lurking behind.




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Fig 35. The YPVS servo. Undo the two gold allen bolts to take the cover off.




https://imageshack.us/a/img841/4386/36servo.jpg
Fig 36. Take the front cover off, and remove the large crosshead screw. Now release the cables and pull the black plastic drive horn off. Now you're left with this.




https://imageshack.us/a/img819/5290/37servo.jpg
Fig 37. Finally remove the inner gold allen bolts so the cable bracket comes away from the engine. Put the allen bolts and gold screw back in for safekeeping.




https://imageshack.us/a/img825/766/38servo.jpg
Fig 38. YPVS components showing the cover and the plastic drive horn. Note that the cover is stamped Moto Minarelli.


Twistgrip and throttle cables



https://imageshack.us/a/img29/9674/41cables.jpg
Fig 39. It is far too much hassle to remove the cable from the oil pump (you can't do it with the engine in anyway) as well as dismantling the cable split. The lengths are set at the factory and messing with them will upset the oil delivery. The less you mess with this the better, as a lubrication failure will instantly wreck a rebuilt engine. The best method is to remove the throttle cable at the twistgrip end and take the whole lot off the bike with the engine.




https://imageshack.us/a/img853/5291/42twist.jpg
Fig 40. Dismantle the twistgrip by removing the allen bolts holding the housing together. Also remove the bar end by unscrewing the large allen bolt in its centre.




https://imageshack.us/a/img850/8153/43twistbits.jpg
Fig 41. The twistgrip bits. The correct one for this bike is the 70-degree quick-action throttle, although sometimes standard TZR ones find their way onto these bikes.




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Fig 42. Pull the throttle cable through the frame so it exits the left side. Ensure that the junction box is pulled from out from its rubber collar and is free to move with the engine.


2T tank


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Fig 43. Now to the oil tank. Remove the bottom retaining bolt from the oil tank. LOOSEN but do not remove the top bolt. The oil tank should remain on the bike until the last possible moment to stop the risk of debris entering the oil circuit.




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Fig 44. Remove the oil tank pressure line.




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Fig 45. Undo the oil level warning light by disconnecting the 3-way connector block. It's located just under the frame above the oil tank. Also remove the HT lead from the sparkplug and the temperature sender cable from its pin on the cylinder head.




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Fig 46. IMPORTANT Debris or dirt in any part of the oil circuit is usually fatal to the engine. Extreme care must be taken to prevent dirt ingress. Clean the underside of the oil tank and oil cable. Undo the circlip and pull the cable off the bottom of the tank. Drain the 2T oil into a suitable container (it can be re-used)




https://imageshack.us/a/img14/4291/48coilpipe.jpg
Fig 47. Carefully clean the end of the pipe ensuring no contamination enters the pipe. Use cotton buds to clean the outside edge, then block up the pipe with a bung or similar.




[img]https://imageshack.us/a/img69/3006/58dstuffit.jpg
Fig 48. Pipe sealed with tissue.



Engine removal



General Notes
Engines are heavy and usually their centre of gravity is not where you'd expect it. On an engine with a cradle, I believe it is best practice to use the 'three points of contact' rule to ensure that the engine does not fall off the bike. On the TZR, where the rear of the cradle extends backwards above the shock, it cannot be lowered vertically as the crankcase will impede on the frame as it comes out (and in all likeliness would fall off the jack). Therefore the engine must be rotated forward and down so the rear of the engine swings free of the frame. Additionally by leaving one contact point attached it greatly reduces the risk of an accident.



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Fig 49. Remove the right-hand radiator mount bolt.




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Fig 50. The radiator should now be free to be pushed forward. The engine can only clear the frame and rad with this done.



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Fig 51. The correct position for a trolleyjack when removing the engine with the bike on the sidestand. Note that it is slightly to the right (to counterract the bike leaning left). DO NOT allow the jack to rest against any part of the starter motor. The big bolt on the engine casing is the drain screw. This position will also work if the bike is on a paddock stand. Wind the jack up so that it contacts and supports the engine, be careful not to unload the suspension.




https://imageshack.us/a/img197/3761/49cabstay.jpg
Fig 52. There is a cable bracket on the RHS of the frame to the rear of the engine which prevents access to the top engine mounting bolt. Undo and remove. Also note there are several hoses which are below the carb, make sure they will not impede on the engine rotating forward.




https://imageshack.us/a/img15/1221/50topbolt.jpg
Fig 53. The location of the top mounting bolt. The cradle is the black steel frame, and cannot be removed with the engine on the bike. It is just behind and above the kick start plug on the RHS of the engine casing.




https://imageshack.us/a/img826/1236/51drivetop.jpg
Fig 54. Use a pair of spanners to undo the top mounting bolt, then use a long screwdriver or drift to drive out the bolt. It barely clears the frame but will come out.




https://imageshack.us/a/img839/6478/52topboloff.jpg
Fig 55. The top mounting bolt. Note the position of the flat and spring washers.




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Fig 56. Unbolt and remove the LH and RH side cradle mounting bolts.




https://imageshack.us/a/img15/1300/54rotfwd.jpg
Fig 57. With only the bottom bolt in place we should be able rotate the engine forward and down towards the ground, by lowering the height of the jack. If the engine does not move, then it will be necessary to loosen the lower bolt.




https://imageshack.us/a/img38/6299/55botbolt1.jpg
Fig 58. With the trolley jack supporting the weight of the engine, use socket and spanner to loosen the lower mounting bolt. If the engine has not rotated forward and down to the correct angle as in Fig 57, now is the time to do that.




https://imageshack.us/a/img15/1727/59drivebot.jpg
Fig 59. Drive out the bottom bolt using the long screwdriver. Keep the screwdriver in the hole as it provides a pivot point for the engine and assists in controlled lowering.




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Fig 60. The removed top and bottom mounting bolts. Note that they are very different!




https://imageshack.us/a/img23/4820/61lower1.jpg
Fig 61. Continue to lower the engine using by dropping the trolley jack. Pay particular attention to the radiator/head clearance. The top hose will assist you in preventing the head from striking the radiator.




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Fig 62. During the procedure lower a little at a time. Mentally do pause-stop-think-continue. CONSTANTLY check that nothing is snagging the engine as it rotates forward and down.




https://imageshack.us/a/img543/3037/64lower.jpg
Fig 63. The trolley jack is now fully down with the engine supported by the jack and the long screwdriver in the lower bolt hole. The head is clear of the radiator and the weight of the engine is directly central to the jack.




https://imageshack.us/a/img202/6748/65lowerf.jpg
Fig 64. Whilst supporting the engine with your right hand, withdraw the screwdriver from the lower bolt hole to release the engine from the frame. If the carb is full of petrol then this will spill through the exhaust port. Some additional water might also come from the water pump housing.
____________________
GSXR400 x2 | '94 RVF400 | '93 TZR125 4DL (again)
20:22:30 BLUEX5: i would love to be forced to undergo a**l plugging with different sizes
20:48:18 Temeluchus: comp you hunk of smouldering homos3x you

[Timmeh]

The next exciting installment will be taking head off and checking the top end, will also include some horror pictures of my own engine.


____________________
GSXR400 x2 | '94 RVF400 | '93 TZR125 4DL (again)
20:22:30 BLUEX5: i would love to be forced to undergo a**l plugging with different sizes
20:48:18 Temeluchus: comp you hunk of smouldering homos3x you

[Irezumi aka Reuben]

Ho much did the bike set you back out of interest?
____________________
Pictorgraphicalfantastical

[Timmeh]

[nealefoulds]

What a handy guide ...

I just purchased one in bits so your pics will help a whole lot with my rebuild. thanks dude.

[salem1987]

great guide! looking forward to the next installment

[RhynoCZ]

That looks like you're having fun.
____________________
'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Wabby]

Looks like you are having fun.

Now you have a 4DL be prepared to pay over the odds for the specific parts that only fit it, and take many many months sourcing certain other parts.

On a plus note: A photo whorage opportunity for my old trusty (not) steed.

https://img167.imageshack.us/img167/1507/sta41688lw5.jpg
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https://img390.imageshack.us/img390/6466/sta41704wt6.jpg
https://img71.imageshack.us/img71/4561/sta41708lg8.jpg

And just to rub it in, I only paid £820 and it was running and in that condition when purchased (minus the damage to the front fairing, my old man did that falling through the Garage roof. lol).

Enjoy your time holing pistons and pissing about with reeds / carbs / YPVS etc. - It certainly passes the time.

BTW - I also have an extremely rare workshop manual for the 4DL. I will try to find it on my hosting for you and link you to it. Saves loads of time with certain aspects.
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What restriction?

[glxious]

nice!! i have one like this. could you please take some photos of the front engine bracket. that whci is for the radiator too.. mine is cut, because an idiot previous owner wanted to fit an 1kt motor on. is there a thread with whole restoring?