HRC VF400RK TT F3 Replica.

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colinf
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Bike owned: VF400RK, TRX850 , Bultaco T350
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Re: HRC VF400RK TT F3 Replica.

Post by colinf » Tue Aug 22, 2017 7:36 pm

Haven't had much time for hands-on work on the bike for a bit but i have been looking for parts and doing a bit more research online. I really wanted to get a rear wheel for it so i can check clearance issues and chain run etc.As stated before ,according to the translations online,the Honeybee bike uses a CBR400F rear which is 18".These do seem to be available on Yahoo Japan ( and reasonably priced ) but they all seem to have 6 bolt discs fitted unlike the 3 bolt set up on the racer. I think an NS400R rear would be a good compromise as its got the three bolt disc but 17" not 18" diameter so might need to experiment with gearing/tyre size. I had contacted the NS400 forum because there is a trend of changing wheels for bigger tyres, and also of putting VF1000R rims on NS hub & spokes, to see if anyone had a spare standard rear and also contacted classic race replicas to see if they had any in stock,asked if they ever came across CBR400F ones while i was at it. Ian at classic race replicas said he knew of them but have never seen one but he did point out that '86/'87 RS250 Hondas used the same style wheel in 18" rim size. but are probably even rarer!
This got me thinking so i googled RS250 rear wheels.........nothing! but i did find a website for Gecko motorcycles who had a rear disc for one and it's a three bolt one with the same pattern drillings as the Honeybee bike.So i went through my notes from the translation about the Honeybee bike and it said that the "CBR400F" rear wheel is 18x3.00
Now, according to my research the CBR400F has a 100/90 18 tyre on the back and given that the NS400 front was 100/90 16 on a 16x2.50 rim i think it's highly unlikely that its a 3.00 rim. I now think the Honeybee bike probably used an RS250 not a CBR400 one.

ligurt
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Re: HRC VF400RK TT F3 Replica.

Post by ligurt » Wed Sep 06, 2017 9:53 pm

HI Colinf, Im back after monthes and could happily see your project is moving in the right direction. Yes indeed, rs250 seems to be intresting to cannibalize for the vf. I have now the 1983 RS250 rear shock mounted on my vf400f with the harder HRC coil for that bike and works very very well, we have relocated the bottom attach and built a new upper one, I'm really satisfied and also have the opportunity to lift the back side from -3 to +3 cms to fit the 18 inches or the magtek 17. Have you discovered something concerning the HRC Honeybee rear shock?

colinf
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Re: HRC VF400RK TT F3 Replica.

Post by colinf » Sun Sep 10, 2017 12:49 pm

Good to hear from you.Apart from searches on auction sites i haven't done anything regarding the shock.Think even the racer retained stock mountings.Think i'll go with an NS400R rear wheel ( when i can get one ) which could be replaced at a later date with an RS250 one if one came up. The NS wheel would need a wider tyre fitted to compensate for the smaller diameter while maintaining the profile.Obviously the smaller diameter means a loss of speed.........but by how much?
I found a couple of useful websites,one to calculate the overall diameter for a given tyre size and the other to calculate theoretical top speeds for given tyre diameter. The top speed doesn't take into account efficiency or lack of it due to wear or drag etc but all i needed was a comparison of the 17" 120/90 and 18" 110/90 wheel/tyre set ups. I wont bore you with the equation ( unless someone wants it ) but you need to know the RPM of the engine,the primary drive ratio,top gear ratio and final drive ratio as well as diameter of rear wheel .The top speed it came up with is higher than the bike would manage ( unlikely to redline in top etc ) but i did the calculation several time with different revs and gear ratios and the difference remained the same, it amounts to a loss of 1.5mph flat out in top.
Got three leads for NS400 rear wheel at the moment so fingers crossed!

ligurt
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Re: HRC VF400RK TT F3 Replica.

Post by ligurt » Mon Sep 11, 2017 6:43 pm

I guess you are referring to this site. Am I right? If not I found it very useful:
http://www.gearingcommander.com/

colinf
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Re: HRC VF400RK TT F3 Replica.

Post by colinf » Mon Sep 11, 2017 7:46 pm

I did look at that one but wasn't the one i used.I'll check my notes when i get a chance and i'll let you know.

ligurt
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Re: HRC VF400RK TT F3 Replica.

Post by ligurt » Thu Sep 14, 2017 10:36 pm

colinf wrote:Good to hear from you.Apart from searches on auction sites i haven't done anything regarding the shock.Think even the racer retained stock mountings.Think i'll go with an NS400R rear wheel ( when i can get one ) which could be replaced at a later date with an RS250 one if one came up. The NS wheel would need a wider tyre fitted to compensate for the smaller diameter while maintaining the profile.Obviously the smaller diameter means a loss of speed.........but by how much?
I found a couple of useful websites,one to calculate the overall diameter for a given tyre size and the other to calculate theoretical top speeds for given tyre diameter. The top speed doesn't take into account efficiency or lack of it due to wear or drag etc but all i needed was a comparison of the 17" 120/90 and 18" 110/90 wheel/tyre set ups. I wont bore you with the equation ( unless someone wants it ) but you need to know the RPM of the engine,the primary drive ratio,top gear ratio and final drive ratio as well as diameter of rear wheel .The top speed it came up with is higher than the bike would manage ( unlikely to redline in top etc ) but i did the calculation several time with different revs and gear ratios and the difference remained the same, it amounts to a loss of 1.5mph flat out in top.
Got three leads for NS400 rear wheel at the moment so fingers crossed!
Here it is what you're looking for about the rear wheel, it's the same as the HRC cbr400f wheel:
CBR400F/NE5
リヤホイール
84" 42650-NE5-750 3.00-18(VF400R/NE4共用)
85" 42650-NE5-000 3.50-18
coming from:
https://blogs.yahoo.co.jp/okatasi2004/f ... .html?m=lc

colinf
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Re: HRC VF400RK TT F3 Replica.

Post by colinf » Sat Sep 16, 2017 10:45 am

Thanks for that,what a great link.I can't believe the difference in weight between the the road comstars and the magnesium HRC ones!

ligurt
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Re: HRC VF400RK TT F3 Replica.

Post by ligurt » Sun Sep 17, 2017 9:08 pm

Cpolin what do you referre to? I couldn't see any data on the wheels weight.
Please let me know.

colinf
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Re: HRC VF400RK TT F3 Replica.

Post by colinf » Mon Sep 18, 2017 5:08 pm

When i checked the link from a PC it was all Japanese text but doing it on my phone it comes up with the option to translate the text.It was in between the pics of the Comstars and was in the section "NS racing Comstar".

colinf
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Re: HRC VF400RK TT F3 Replica.

Post by colinf » Sun Dec 10, 2017 4:23 pm

Didn't get much chance to get on with the bike in the Autumn.Delays in building the bike shed extension and helping out a friend who's recovering from serious bike accident.The bike involved was written off but his injuries mean he's selling off his other bikes.He wanted his BMW K1100RS outfit prepared for a local classic auction, this involved changing the clutch after removing sidecar and subframe! Turned out the crankcase was leaking water so it was stuck in the shed for a while.Also "adopted" a Laverda Mirage for a mate who's wife doesn't know he's got it,once recommissioned i'll be able to ride it in the spring. But........getting back to the build i finally got hold of an NS400R rear wheel , many thanks to Ian at Classic Race Replicas. Getting sprocket carrier and a disc for it as well as the rear caliper and mounting bracket for a VF500 so i can start checking for alignment issues and chain run etc The wheel fits the VF400 spindle which is a good start, i may nip round the local independent bike shops to see if anyone has an old 120/90 tyre in their pile that i could put on it while i set it up.


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