new RC390 cup owner - track toy

Alibee071290

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Hi All.

i purchaced a RC390 Cup off ebay during lockdown here in the UK (May 2020) and set about tuning and setting it up and painting it. i got a couple of trackdays in before the weather got to grim.

it has some trick goodies like a HM GP quickshifter (up for sale) and a HM M3 dash, and is pushing out 44rwhp after being set up.

im continuing to modify it in any way that will lower weight and make it more of a weapon in the corners, im tempted by some lightweight wheels but i want to keep to a 140 on the rear as it turns in so well !

any thoughts on how to make it more of a weapon, please let me know
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kostean

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Throw off the 520 chain- this is a major HP killer. On racing we go on erz 415- but you need to change these -5-6 sets a season and this is for juniors who are light. Else 390 CUP bikes are good considering the price/racing setup they have, but have major reliability issues. Head gaskets, breaking seat supports, shifting rods, cooling...and the list does go on and on. For serious racing, you need to have 2 of them with you all the time.

140 rear tires are good- go better in on corners, though 150 lets to have a bit of more rubber at the road.


Alibee071290- does HM M3 dash on Rc390 show gears as well?
 

kostean

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Ah yeah- for making it a "more track weapon",
* get RC cover protectors as these have saved the alternator and clutch covers on countless slides.
* Front fame holder- original is made of glass, and heavy as heck, there are aluminium aftermarket ones available.
* Rear wheel center hub can be drilled and slide pools installed like at the front wheel.
* Steering stop to be installed (has to be aluminium), so it softens the hit to tripple clamp on crach (tube anyway bends and better to keep the grip on nut not too tight)

* short intake funnel at the angine
* oversized injector
* fully programmable ecu and AFR module

anyway, the principle is to make it as "slidable" as possible, as any chanse on racing against kawas etc on these things is corner speed and phyiscs sets its limits.
 

Andy

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Whats the M3 dash like? I've been thinking about one of these.

Obviously sort suspension and weigh loss but if it's a Cup bike that's probably done?
 

Alibee071290

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Hi All , thanks for the advice, ive done most things.

switched the WP suspension out for K Tech all round.

Im not getting on well with any of the HM equipment, i removed the quickshifter and replaced with a dynojet, and im not happy with the dash. HM customer support and trouble shooting terrible, they dont want to seem to help at all. their ethos of plug and play with limited instructions really doesnt work well when the items are not working as intended.

the M3 dash should display gear position, and it has at some points, just never when ive actually wanted it to! it calculates it from RPM and wheel speed i believe rather than the gear position sensor (i found this out after i replaced the sensor!)

i would recommend save your money and stick with the standard dash and a stopwatch.

im contemplating a BST front wheel and a Marchesini rear. to keep sizes as close to stock as possible (2.75 front and 4.25 rear). just waiting until next year to bite the bullet.
 

kostean

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Yeah, as far as I have seen on the track, with 390, even the modified ones, they are running stock dash as there simply aren't good alternatives what would just plug in. Gear indicators reading between wheel sensor and RPM are available, but then you need the sensor at the front wheel and are still innaccurate in comparison with built in gearbox sensor.

The KTM own SSP300 kit had the Koso dash what really helps to follow RPM, but the downside is that you miss the gear indicator, and apparently even the aRacer race ECU can not get the gear position from the inbuilt sensor and there are no converters as well available. All-n-all, going for a Koso dash even when missing gear numbers would make sence, but then it is the support frame what is missing and these were produced only for SSP300 kit and can not be separately purchased.

 

Alibee071290

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yeah, and the M3 dash is tiny ! so the RPM gauge is not great, even when you have the display filling the screen. i end up only using the dash for noise testing. im not using any of its features as it works to intermittently

if i come across a standard dash im going to get rid of the M3, its not worth the hassle for an individual rider.
 

Pj19

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Nice bike you have there!
If I may ask, why did you switch to K-Tech from the WP suspension?
 

Alibee071290

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Nice bike you have there!
If I may ask, why did you switch to K-Tech from the WP suspension?

I needed it set up for my weight, so I would have needed new springs. also in an attempt to recoup some money, selling the WP and going Ktech will hopefully earn me a profit
 
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