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Rebuilding NSR 150 SP

Discussion in 'Modifications and Projects' started by R Moore, Jul 19, 2008.

  1. Hello viewers,

    Recently my NSR 150 SP developed a noisy gear box, especially in 2nd and 3rd gear. Rather than continue riding and risk further damage I decided to strip the motor. I have rebuilt a number of bike and car motors over the years so I have the confidence to do it. There are some traps to working on small alloy motors which can be fragile when applying force to separate cases, remove stuck bolts and remove bearing. The main problem I found was steel bolts often weld themselves to alloy after a few years and some of the crank case bolts joining the two halves together are only 8mm A/F (6mm thread). I also find the bolts may be overtorqued by the factory when they assemble with air tools. Two bolts broke but luckily I should be able to drill them out and re-tap the threads. Two stokes are relatively simple in that they have no valve gear but the transmissions are the same as any other bike. The clutch on the NSR is very robust for a 150 cc motor. After 25,000 km the plates are still within standard tolerance for thickness. In hindsight I should have used an impact driver on the eight mm bolts. As I suspected, 2nd and 3rd gear show major pitting and breakdown of the case hardening. The Counter shaft bearing on the sprocket end is rough as well as the layshaft bearing on the clutch end. I will replace all the bearings and seals. The shift drum and shift forks show little wear. The clutch basket is in good condition and the steel plates show no warp and only minor scorch marks on one (from drag starts).
    The crank bearings are serviceable but I will replace them as well as the seals. The piston has moderate wear and is still within service limits but I will replace with standard "B" piston and rings. The bore shows some scuffing but not enough to justify $400 for a new Nickle Silver coating.
    I note there is potential for improving the ports and the power valves as the casting and machining is a bit rough. I would not expect big gains but if it's free I'll take a little extra performance. The exhaust port had small build-up of carbon and the combustion chamber was nearly carbon free.
    All up I think it's about 10 hours to remove and dismantle the motor and should be about 15 hours to rebuild. I'll take it slowly as I haven't had my hands in an engine for a while. I'd rather do it right the first time than have to strip the motor to rectify a mistake.
    I keep you updated on progress. I figure it will probabable cost about $300 including a couple of special tools that I bought. I am pleased I didn't need any Honda special tools as just the flywheel puller was $166 retail. I modified a $20 Super Cheap gear puller to do the job plus I applied some heat from a hot air tool used for paint stripping. The most expensive item so far is the impact driver and allen key adapter at $67.
    The bearings will be SKF or Timken. These may be better than the originals and cost less than Honda parts. I still haven't separated the right crankcase half from the crank and bearing and may have to get it pressed out.

    Bob Moore
  2. There are pics in the workshop manual.
    The workshop manual is avialable elsewhere on this forum.
    Do you think it worthwhile posting images of a dismantled single cylinder 2 stroke motor? Perhaps the broken bolts, worn gear teeth and adaption of the gear puller to remove the fly wheel may be of interest to some owner/mechanics. I don't have a high resolution camera and I can't do decent close-up shots. I may be able to borrow a better camera for some close-up shots then post in the next few days. It could be up to a week before I get the parts.


    Bob Moore
  3. This looks like it will be a good thread, keep us up to date and take some pics if possible :grin: Cheers and good luck
  4. I managed to get some images and I hope they are clear enough.
    After cleaning off the oil and examining the gearset in more detail, it seems 2nd 3rd, 4th and fifth gear cogs on the layshaft need replacing.
    2nd is the worst, then 3rd, 4th and 5th. This makes sense as the launch in 1st is softened by slipping the clutch and also the time in 1st is relatively brief. Second gets the biggest hammering then the force through the gears gets less as high ratios are selected. The layshaft or driving gears rotate at a higher speed than the mating gears on the countershaft or output shaft. Consequently the layshaft gear, for instance in 2nd, rotates at 31:16 so will wear at almost double the rate of the mating countersaft gear. I see that 4th shows copper colour and this means the case hardening has worn through and the next stage is pitting and accellerated wear. 5th is showing early signs of this. The gears on the countershaft are slightly worn but serviceable. I will have to see how much these gears are going to cost before replacing any on the countershaft. I will replace all bearings and seals. I suspect a spacer was left off the end of the countershaft during factory assemble. The second gear cog on the countershaft would have too much lateral play and may have accelerated the wear of the gears.






    The image of the complete gearset shows some of the copper colour mentioned above. Some may ask why has my gear box s**t itself?
    Good question. I can only presume that it's hard riding over an extended period and increased output from the performance mods. I changed the gear oil every 6,000 using quality oil of the correct grade. I don't know if a spacer missed on assembly would cause premature failure.
    I'll post more stuff if relevant. I can order the gears tomorrow and the bearings can be purchased from any good supplier such as CBC. fortunately bearing makers have agreed to standardisation of bearing specs with a code number stamped on them. There is only one bearing out of 8 that has no code.
  5. seriously cool pics, mate :cool:
  6. Gear prices

    I made an enquiry at my local Honda dealer about replacement cogs for the worn items above. Just a rough estimate was minimum $50 for 2nd gear on the mainshaft up $200 for 1st gear on the countershaft. He said all up it could be $2000 to replace the lot. It is Action Motorcycles (don't start!) so I may ask my son-inlaw to check these parts prices as he is a parts interpreter for a multi-franchise car dealer but has access to the Honda bike database. The alternatives are gear repair and rehardening or second hand from wreckers. I could also enquire with my contact in Thailand to see if it's feasible to buy from there either new or used. Of course if use, the risk is the gears are no better than what I have got.
  7. i have the honda EPC...heres some figures for you
    23431-KW6-840 counter shaft 2nd 29.90+ tax
    23451-KW6-840 counter shaft 3rd 29.90+
    23481-KW6-840 counter shaft 5th 60.98+
    23411-KW6-840 counter shaft 1st 33.18 +
    23461-KW6-840 counter shaft 4th 29.90+
    23501-KW6-840 counter shaft 6th 58.44+
  8. 23471-KW6-840 5th mainshaft 29.90+
    23441-KW6-840 3rd/4th mainshaft 59.19+
    23491-KW6-840 6th mainshaft 29.90+
    23421-KW6-900 2nd mainshaft 34.29+
    $453.40 retail inc gst for all of them
  9. And they want 2g, :evil: :evil:
  10. It was for all gears on main and countershaft plus shafts. The guy in Action Parramatta spares just quoted the 2g figure off the top of his head. There is a guy in a Liverpool wrecker doing a search for new spares and perhaps a complete second hand motor. If I can get a good second hand motor at a reasonable price it will be source of good spares or I can rebuild it to have a complete motor ready when this one dies in a few years.
    Thanks for all the part numbers and prices fellas. I hope the bikes not off the road long as it's boring in the car although it's much warmer.
  11. NSR rebuild delayed another couple of weeks waiting for parts. I purchased the bearings from CBC bearings just off Silverwater road in Sydney (around the corner from the bike wreckers). I couldn't get the seals so will have to add to my existing order from Action P'matta. The Honda spares guys at Action M/C have been helpful although they are hamstrung by parts policies in the motorcycle industry. I found the parts prices vary from dealer to dealer. I've ordered 3rd-4th mainshaft cogs and will reverse 2nd gear on the mainshaft so the teeth faces that have little wear are now the drive faces. Second gear is not in stock and would have to be back ordered (from Japan) with a wait of 3 - 4 weeks. When they quote "in stock" it means at Honda Australia, not on their shelves. They tell me they carry no genuine parts on shelf, only what customers have ordered and have not collected. They only carry stuff like air filters, plugs and tyres. Todd at P'matta Action told me that generally, Honda Japan supports models for up to 10 years after release and will only continue producing parts after that for models that are in high demand. He said that parts for the nsr 150 may become hard to get within the next few years. I had conversations with a number of motorcycle wreckers and they have customers who will purchase any nsr engine that comes in. The motor is in high demand because they wear out relatively quickly. In was mentioned by several wreckers that gearboxes are a common problem because incorrect maintenance information is given to the owners by Honda. They say that with the gearbox oil showing at the half way mark in the oil level window, there is a shortfall of 0.4L or half the gear box capacity. They say that low oil level, combined with cheap oil and hard riding contributes to gearbox failure. I can't verify the accuracy of these comments until I see for myself. What I would do is just add 0.8L for a fill after rebuild (0.76L for change) and not judge the oil level on the sight glass.
    One wrecker said that if he got an NSR with a damaged cylinder or worn top end, he would rebuild it as he could get over $1,000 for a complete engine in good condition. Another wrecker said he has a number of customers who will pay $1,200 for an engine. The same wrecker confirmed "gearbox meltdown" from low oil levels was the biggest cause of failure of NSR gearboxes. He also said that if I stacked my bike he would take it! Talk about vultures.
    I have a theory about why my gearbox has failed but I'll share that with you later during rebuild. Bearing prices from CBC were about 30% less than Action M/C with the same or better quality. There was one non-standard sized bearing (Honda proprietry) but it is one that has little wear so I just put it back in.
  12. Just a word of warning with the aftermarket bearings. Make sure you order the ones with the correct clearance. That's what the C-# is at the end of the ID #. You wil find that the bearings on the flywheel side of the crank run a larger clearance than the primary gear side. For example a 6205 C1 will have less clearance than a 6205 C3 but still have exactly the same physical dimensions. Cheers
  13. Thanks for the info.
    I took the old bearings with me and all the codes are identical including the clearance suffix on the main bearings.

    Bob Moore
  14. You going to do a rod kit while you're that far into it? The extra bucks spent now could save a heap of time & frustration later :wink: :wink:
  15. I'm thinking about it. The rod small end is in good nick all other wear dimensions are well within standard tolerances. I'm trying to keep costs down and I would have to get the crankshaft to a workshop with a press. Unless I get someone who will do it for $50, it's out of my budget. Yeh I am in two minds as I know it would be a pain in the arse to split the cases again if the big end bearing collapses in the near future. However there are no signs of this and the bearing has little wear and no roughness.

    Bob Moore
  16. Second gear was stuck on the countershaft with a damaged sleeve so I had to cut the gear off. Now have ordered 16T 2nd gear (mainshaft), 31T 2nd gear (countershaft), 5 oil seals, 3rd-4th gear (mainshaft), spacers & sleeves. I have 5 new bearings. I will get a new standard piston and rings. The bore has minor scuffing and is within wear limits.
    Todd at Action M/C tells me there is a 4 - 6 week wait on spares. Still waiting for my contact in Thailand to respond to spares queery but said he will email tonight. In the mean time not much I can do except cut my own gaskets & clean up the ports and power valve. It will be interesting to compare the cost of spares from here to Thailand as I have all the prices from Action M/C. My contact in Thailand recons the genuine Honda spares are half the price of parts in Australia.
  17. NSR 150 rebuild update

    Parts from action P'matta were available quicker than I expected as the back ordered parts were quoted as 3 - 4 weeks but arrived after 8 days.
    I saw the great prices from Taiwan for genuine Honda NSR parts so I have ordered the rest of the gear box internals and a cylinder kit. The parts from Taiwan are about 50% of the price charged by Action M/C.
    Some hold-up in the Taiwan parts due to Thai public holiday and supplier off on trail riding in mountains. When I get all the parts, I'll start putting the motor back together and post step by step assembly pics. I'm incorporating some addition modifications so I hope to a bit more power. I think a spacer was left out in factory assembly and that is what contributed to gear failure. All up for a near total engine rebuild it has cost $505. I would hate to think what labor would have been but probably $800 at least.

    Bob Moore
  18. Some discussion re NSR parts from Thailand

    My NSR 150 supplier in Thailand tells me that Honda Thailand stopped productions in 2000. The model never sold well their because of it's relatively high price. It was, and perhaps still is, the king of the small high performance street "racers". There were a large stock of NSR's in storage and Australia was the market selected to get rid of them. The stock ran out in 2005, I am told and also 2 strokes are being phased out in most markets. I would expect that parts stocks may run down over the next few years. It's not expected that most NSR 150's would last beyond 10 years and many may be on the scrap heap well before then. They are a relatively high stressed motors with 150 hp/liter and when the coating wears off the bore, the repair cost may be too high for many owners. I quite like my NSR despite it's short comings in the braking and chassis. I intend to keep it on the road for as long as I can and will expect to rebuild the engine every 30 - 40,000 km. I will need to stock up on parts from Thailand before thay become unobtainable. I hope to build a spare motor so I can just rebuild at leisure and just swap the motor over rather than having it off the road for a few weeks (or months in this case).

    Bob Moore