DEFINITE Big Bore for J-Engine

sam2019

sam2019

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The J-Engine is used by the Hunter, Meteor and "new classic" - so quite a few models. whether the classic ever makes it to the west is doubtful but the Meteor is already there and the Hunter really is a nice cheap beginner's bike. Consequently I used the opportunity of a bike with seized piston to measure the engine opening and got me a cylinder set with piston to check the measurements.
Racedynamics offers the PT4 for all these models so fuel management should be working and the aftermarket offers open exhausts and different air filters.

Especially the Hunter is a good looking little bike that already is quite lively (for 20 BHP) but could easily use another 10 BHP for the brakes it has and riding stability.
As of now top speed is 115 kmh but my guess is 140 would be well within save margins. Which would make it usable on the Autobahn LOL.

Stay tuned for more exiting stuff :)
 

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Nice comparison table UCE vs J-type - although they got the 4 vs 5 speed wrong in the UCE section
 

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There seems to be some severe cheating going on at RE with the J-Engine proposed power output. I know, dynos can vary - but still:
 

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This is kinda confirmed by Hitchcocks dyno run, although they just wanted to see if a free flow air filter makes a difference:
 

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Preliminary measurements show the piston pin has exactly the same diameter as the Hima piston and the distance from top of piston to bottom of pin is also exactly the same. This means I could use the many Hima OEM pistons I have collected to make a Hunter big bore. Lets see what that gives us:

OEM: 71.5mm dia
1701089282332.jpeg

Himalayan 77.5mm dia
1701089401648.png

OK, 400cc - not earth shattering I guess but cheap. not considering the PT4 I might need to buy. Or maybe the OEM ECU can balance that? @Sasa - what's your take on that?
 
More good news, at least preliminary (I love that word!)
I have ordered quite a few 84mm pistons for the 477 Himalayan Big Bores. I am a bit nervous about future prospects with the classic Hima now out of production and the new Hima having 40HP already.
But as it seems that same piston put into a Hunter would result in a nice 475cc engine which in keeping with good italian/japanese tradition I would call 500 :cool:

I have to figure out if 5.60mm is enough thickness for the liner though - OEM has 6.70mm
I also have to assume that the engine body opening is consistent over the entire production cycle so this 500cc set remains plug&play

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sam2019 said:
There seems to be some severe cheating going on at RE with the J-Engine proposed power output. I know, dynos can vary - but still:
Click to expand...
You're still mixing cranckshaft data (which is what manufacturer provide) with rear wheel data, which is what the dyno will provide. There is always a good 8 to 15% of loss between crank and rear wheel, factor in the differences between dynos and you get that.
 
Sasa said:
You're still mixing cranckshaft data (which is what manufacturer provide) with rear wheel data, which is what the dyno will provide. There is always a good 8 to 15% of loss between crank and rear wheel, factor in the differences between dynos and you get that.
Click to expand...
I understand the difference between RWHP and BHP - but the difference between 22 and 15 is 33%
 
sam2019 said:
I understand the difference between RWHP and BHP - but the difference between 22 and 15 is 33%
Click to expand...
But the stock is 20.2 at crank, and he measured 16.18... -20% which is not -33%, and certainly more than possible, taking in account different conditions like fuel, air temp, different dynos etc...
 
Sasa said:
But the stock is 20.2 at crank, and he measured 16.18... -20% which is not -33%, and certainly more than possible, taking in account different conditions like fuel, air temp, different dynos etc...
Click to expand...
I was wrong with 22 - it is only 20.2 BUT Hitch measured 15.17 with OEM configuration. The higher value was with mods on air and exhaust.
so 25%. That seems a bit high IMO but then again as you said different dynos may account for it.
 
Unfortunately the 400cc version ran into a problem: initially the measurements showed the OEM liner to be thick enough that boring/honing could be done with that same liner in place - but RE decided to use a liner inside another liner which together form the entire thickness. After boring the inner liner became too thin - so we had to press the entire liner combo out and replace it with a new liner. The many liners I have in stock (which would have been cheap) did not fit and a new liner had to be ordered from Delhi - this all added 100% to the price tag.

I still had it done for a test ride to see how the OEM ECU will handle it - and if necessary add a fuelx pro to the mix.
 
Bought a Hunter today with only 8000km on it. A nice bike for a youngster (a bit much of a forward leaning position for my taste - but nice acceleration as it is). This one will get the experimental 400cc engine next week. Later (possibly next year) this will be followed by a 500cc engine.
 
400cc engine runs great without any additional ECU changes, no fuelx or PT.
Oil thermometer added and to adapt it to my personal preferences extra lights, a high handle bar plus a carrier for OEM panniers will be added, voltmeter and 12V plus for charging as well. Lets see if i can get it to be a fast travel bike.
 
sam2019 said:
400cc engine runs great without any additional ECU changes, no fuelx or PT.
Oil thermometer added and to adapt it to my personal preferences extra lights, a high handle bar plus a carrier for OEM panniers will be added, voltmeter and 12V plus for charging as well. Lets see if i can get it to be a fast travel bike.
Click to expand...
Pics would be Nice
 
Dool said:
Pics would be Nice
Click to expand...

currently not much different from stock on the outside. I am working on a replacement for the 350cc side sticker :)
There is a tachometer on order as well as high handle bar and the oil thermo had to be delayed too as there is no corresponding outlet bold as in the LS410 - but we are doing something, may take a while.
Give me a week and all stuff except oil thermo will be mounted. then pics !
 
So far 5 people have driven the 400 and everybody is surprised by the added agility. The +torque comes on relatively late at 3000-4000rpm but then its a kicker. I am looking for a bigger sprocket to add to the low top speed which would be a big plus on Germany's Autobahns and other assorted highways with large trucks to overtake that run at 100kmh (like they do in Germany mostly). I think I could get it to 130kmh which would really help (up from 115) also because it often is the "suggested speed" at German highways (Richtgeschwindigkeit).
 
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