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Ex All Japan Honda NSR250RK MC18.... or something...


morepower
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So I got the NSR a couple of months ago and only got to ride it a couple of weeks ago.  I know most of the bikes history as I knew, or knew of, the previous owner and that he built the bike from a collection of spare parts and things he accrued over a few years.  The bike looked nice in photos but up close it was not so pretty when you look at the paintwork. But for me I bought it because it was a good base for the bike to be built back into what it could have been back in 1989 as a race bike doing the Suzuka 4 hour race.  The chassis still has the scrutineering stickers on the frame from the ALL Japan series. 
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The frame is an actual RK (Race Kit) F3 version with the extra braces and some added strengthening around the headstock. 
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The chassis differences don't end there with the swing arm being a slightly different extrusion it seems and the torque arm for the rear caliper is the same as the RS250 race bike so the bike is running an RS250 rear disc and caliper set up too. 
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The forks and front brakes are a mixture of NSR, RS and F3 parts. But this is where the main problem with the bike is currently. It seems the springs were the softest Kit springs available and it seems they are progressive springs as the bike dives like it is about to collapse the whole front end but is doesn't quite hit the bump stops. The damping is just too soft and the compression and rebound is just way too fast that it kicks the front back up when you come off the brakes to the point it goes from diving for the apex to wanting to run wide on the way out of corners. It just felt so bad that adding all the pre-load I could to stop it from diving too far made the damping even worse.  So its a case of forks out, get Ktech to check the spring rates and then get a linear spring for my weight and check the valves in the forks and make up some 12.5wt oil which it seems suit the forks the best. Once the front end is sorted the bike should feel a lot more stable and then allow me to push quite a bit harder to then see if there is anything else it needs to get the chassis set up sorted.  

The rear had a HRC link plate fitted the wrong way around so the bike had a dramatic falling link rate so the bike would just get softer the harder you pushed on the rear of the bike. Luckily I spotted that before I rode it and I have added a bit more pre-load on the rear to set up the sag a bit better, but I suspect it will need to be re-sprung too, so that will be looked at when the fork springs go to Ktech.  
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The chassis is the main focus of this winters work on the bike to be honest as the engine is a healthy 64.6 BHP  and does feel nice and strong, although it may need to have the jetting just checked as I think the needles my need to be adjusted as it does feel a little rich part throttle. But the engine will need a few little things sorting to complete the bike though. Not exactly a few cheap things though as I want to build the correct NH3 bottom end to go with the kit cylinders and heads. I can get some crank cases and a crank quite easily but its the gearbox and clutch that is the biggest challenge. So that will just be a case of buying what I can whenever it comes up for sale. Then finally some HRC kit pipes if I can find some. I don't think all of those bits will add much more power and it may see 68BHP if I am lucky I guess. 
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The only other winter job is the bodywork. It has some factory copy NSR race fairing that looks OK but I want to find the correct kit version of the fairing which has a lot more vents and is not exactly the most sleek looking but it would be the correct one for the bike.   I have two options for the fairing which are find the correct one in Japan or buy a Tyga OEM style fairing and cut and chop it around to make it more like the kit fairing. 
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I am also going to get the paint work done and hook up the tail light with some LED bulbs and a switch for a rain light if the bike gets raced at all. 

Looking at paintwork options now too.. I am not going to go down the GP replica route with the usual Rothmans or the normal red white and blue Honda basic design. I want to find something more like the ALL Japan bikes and go down that route. I am avoiding the Cup Noodle paint too I think. The bike was probably just a mid field bike run by a budget team but it was a race bike so I want to keep that down to earth feel for the bike to give it back some of its history. 

I have been looking at these to get a bit of inspiration and I know a few of those are GP bikes so I won't do a full replica  of those designs but they may form some of the inspiration for the finished look.

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I will try to post updates of the bike as I go through it more and do more to the bike. I have two simple issues to sort out and one of them was adding a one way valve to the breather as the bike did spew fuel onto the rear tyre at Snetterton and I had to fit a new tyre at the track. The other is a new or replacement fuel tank rubber as the front rubber is missing.  
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Hope to be out on the bike at a more familiar Mallory park next month as a few places are still available. So I am going to get the forks done as quickly as I can and give the bike one more run out before the end of the year. 

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16 minutes ago, jim157 said:

Lovely. 

 

Obscure TT-F3 paint jobs FTW. 

It has to be done... I don't hate the GP rep thing and the HRC or Rothmans thing is OK if you want to have some road bike as a replica. But this has some heritage and was used in anger in Japan so it was part of that whole era we love. So why not try to make it into something it could have actually been?  The problem is there are so few images of All Japan bikes apart from the top few riders. 

 

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9 hours ago, morepower said:

It has to be done... I don't hate the GP rep thing and the HRC or Rothmans thing is OK if you want to have some road bike as a replica. But this has some heritage and was used in anger in Japan so it was part of that whole era we love. So why not try to make it into something it could have actually been?  The problem is there are so few images of All Japan bikes apart from the top few riders. 

 

Like a few members of the 400 grey bike forum I used to scour yahoo.co.jp for images of the TT-F3 bikes.  There used to be some great blogs showing some really obscure stuff, I don't know if they're still about though. 

Also there were a few magazines that covered the race series: F3 and Racers are two that spring to mind.  They used to pop up on yahoo auctions from time to time. 

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No.57, the blue repsol bike and the O.Jacques elf bike for me! Awesome project!

The vented fairing looks waaaay cooler too. The one that’s on there seems far too high at the front: bosozoku style.

Edited by Doomkinder
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That must be an RS250 rear wheel as well, as nsr's had a 3 bolt disc fitment, i fitted this exact brake set up on my track 21 and used the 3 bolt honda rs125 disc, Dan at Gecko used to sell this conversion kit a few years ago, i still have the pages out the F3 manual with part no's for this kit, but as you say basicaly rs250, ( or rs125 caliper ) with a shorter torque arm.  If i'm not mistaken 11 and 19 are rs250 nx5's, the no 11 RHEOS were a big sponsor in 125gp's around the late 80's early 90's

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  • 4 weeks later...

Forks had the springs pulled and taken to the guys at Ktech. Pulling the springs the first thing I saw was the fork oil was a different colour in each leg. It may not mean the oil is a different rated oil but it makes you think that they need to be drained at least.  The springs were checked and they are progressive springs but not ones that have any relationship to any known HRC ones. 6N initial rate up to 10N for the last 25/30mm and the guys at Ktech said "they wouldn't be nice" and the forks need some linear springs not progressive ones. As the forks are some hybrid things built using a mixture of parts and the damping is just under damped or in the case of the rebound closed right down and just so slow it was packing down or open up 2/3 clicks and it kicked back like a mule (probably worn adjusters), so we are going to look at making up a 20mm piston kit using parts from other kits where possible and then 9N or 9.5N springs and then hopefully it should be good with 5wt oil not the 10 or 12.5wt that many are using in the stock NSR forks. 
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So with the results of the spring test it seems that my feeling that the bike was diving hard but not bottoming out then being fired back up as the brakes were released was 100% accurate. The damping under compression was also lacking and it seems the fork top damping adjusters are worn the rebound damping only has 3 or 4 clicks of adjustment so it is either closed off and too slow to return and was horrible to ride or you open up a couple of clicks and then the forks just rebound way too fast which is also one of the reasons we are looking at the 20mm piston option. If anything it at least confirms I can still feel what a bike is doing and know what is needed to try and fix it and find a set up even if it is for how slow I ride.... 

So next step is pull the forks out, full strip and see what we can do to build a decent fork. If a 25mm piston kit could be fitted it would be great but I think 20mm is more than enough for what I need. 

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On 9/9/2021 at 9:55 AM, Ray Von said:

Lovely jewel like trinkets. 

The 7 stars paintwork was always awesome 

7Stars is an SBK paintscheme. Pointless on an NSR. 

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