Question about Honda VFR 400 R NC30 Motorcycles

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I have a NC30 that has been standing for about a year, the only reason for that is CDI issues. I bought a De-restricted CDI from Japan, replaced the Spark plugs and checked all fuses and connections. I laso gave the carbs a once over (cleaned jets, pilot jets, emulsion tubes, floats and the the fuel inlet ). the bike was running perfect before the CDI busted. Now the bike idols @ between 4000RPM and 6000RPM and does not rev past 8000RPM when cold and 9000RPM after optimal temp reached. Carbs have been balanced and i have checked air screw settings. Could it be the shimming? Running out of ideas. Going to test the CDI today with a VFR thats currently running eliminating that option. Please help...

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Check your CDI on the other bike is a good option. if it was perfect before the CDI change then the new CDI is the only variable.
Wont be shimming.the valves need to wear to change that setting, and the bike has been sitting.
Sounds like its sucking air after the carby once over, but the balancing would have picked that up.
But how did you balance them if its idling at 5000rpm?
Recheck the carb once over,and balance, and make sure the fuel and vacumn tubes are in correct positions. check the throttle cable is replaced correctly
I assume it is running on all cylnders.

Posted on Mar 24, 2011

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I De Restricted my 1981 YZ125 an she still Runs today.

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How to tune / de-restrict a 2 stroke

2 strokes in lower ccs are usualy slow, so heres a list of things you can do to de-restrict and tune your 2 stroke.

1) Get a racing exhaust, Key part too most 2 strokes is a good exhaust, this will remove some restrictions. Gianelli, Big One, fmf and many others are available on ebay or your local bike shop.

2) Big Bore kit, adding a big bore kit can give up to 30% more performance, and will usualy de-restrict the bike. search ebay for (Bike Model) (year) Big Bore kit. it will come usualy with everything you need for the upgrade.

3) Carbon Reed Valves, are a key part too your acceleration, also removing the little cages that stop them opening all the way and replacing with big washers is another good step, make sure theres nothing for your reeds to nock on when removing the cage.

4) Boost Bottle, a boost bottle will help 2 strokes with no reed valves more then reeded bikes but will give alot more low and high end performace. search ebay for (bikes cc) boost bottle.

5) Jets, are a key thing when getting a bore kit or race exhaust. you MUST change the jets if you change exhaust, get bigger ones if you get an exhaust go a few sizes over and check the spark plug if its a brown tan/ grey collor you got it all right, if its black it means you have to much fuel so go smaller, and if its white it usualy means not enough fuel. you can buy jets from any motorcycle shop usualy around $1 a peice. you onyl need to change the Main jet.

6) Air Filter, you dont need it on most bikes but it could add extra acceleration, measure your carbeurator intake and search it on ebay for a K&N style filter, Power filter.

7) Restrictors in the intake, some 2 strokes have restrictors between the carb and the cylinder, it is key to remove these or drill them out to the size of the carb/ cylinder hole size.

8) Sprockets, if your lucky enough to have a chain and sprockets, its a nice trick to change sprockets on your bike.
For Top Speed - Bigger front sprocket & smaller rear sprocket
For Acceleration - Smaller front sprocket & bigger rear sprocket
by bigger or smaller i mean more or less teeth on the sprocket. if you go for speed your acceleration will lack and vice versa if you go for acceleration you will loose top speed.

9) Electical Restriction, Some bikes are restricted in the CDI, if yours does not want to reach a good RPM search up CDI, de-restriction. usualy it involves cutting a wire between the CDI and engine. and will unlock that slow engine into a screaming 2 stroke.

If you follow all these steps your 2 stroke will no longer be restricted and slow and will be the fastest arround.

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Usually the CDI. If you have meet the requirements to operate the bike without the restrictions, then the dealer would be glad to change out the CDI, etc. It is not that costly.
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