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Discussion Starter · #1 ·
My 1990 CBR 1000 accelerates smartly, but at around 5,000 RPM, it really wakes up. I told this to a mechanic and he said that at around 5,000 RPM the needle pulls out of the main, so the bike is mostly running on the main jet. He said that my needle may be lean, to meet emissions, and that I should put in a Dynojet kit, which may wake up the lower RPM.

I've taken apart my carbs many times and have balanced them with my carb stix, so I have no fear of the carbs. Should I just get the kit and install it to see if it wakes the lower RPM?
 

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Do you have an exhaust on the bike or is it stock? Also, my personal preference is Factory Pro Tuning over Dynojet. I think you will find Factory products easier to install and set up properly.

Larry
 

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Listen to Larry...

But you sound like you can handle the carbs. Get a kit and install it. You won't regret it!
 

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the more low end power u can get..the better..u'll have a beast ride if u follow larry's advice!
 

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Wow, I rejetted my bike and I didn't have a clue what I was doing. :) Good to hear your confident with them, but listen to larry, he won't steer you wrong. :dthumb:
 

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Discussion Starter · #6 ·
Larry G: I have stock pipes. I looked at Factory Pro and Dynojet. I liked that Factory Pro included different piston springs, but I also liked that Dynojet made a high altitude kit for my bike. Although the only difference is the main jet and different groove for the needle. All my riding is over 5,000 feet. But I could go with either manufacturer.

Speaking of carb pistons, Honda's are plastic. The get varnish on them which makes them stick. You can spray carb cleaner on the front and back, but they have to come out to clean the sides and top. Usually clears up a stumble.

Shanman: To me, the hardest part of carb work, besides getting the carbs on and off, is removing the dozens of phillips-head screws without stripping the heads. Did you rejet to fix leanness from an exhaust change? Did rejetting make you bike run better?
 

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Sounds like you are comfortable enough with doing the work. Even though they don't necessarily advertise it, you can usually call Factory and they'll put together a "high altitude" kit. Sometimes it is just a matter running a little leaner on the needle and main jet. CV carbs actually do a pretty good job compensating for altitude to some extent so it should only be some fine tuning to make it work right.

If the bike isn't modified, I would start by figuring out why it isn't running clean under 5K. Think about it, you are at high altitude so you have less air and you are blaming it on a lean stock needle. It could just need a good carb clean and minor adjustments, it could be the nature of this bike at high altitudes, or it could be that you need a jet kit.

Larry
 

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No Worries said:
Larry G: I have stock pipes. I looked at Factory Pro and Dynojet. I liked that Factory Pro included different piston springs, but I also liked that Dynojet made a high altitude kit for my bike. Although the only difference is the main jet and different groove for the needle. All my riding is over 5,000 feet. But I could go with either manufacturer.

Speaking of carb pistons, Honda's are plastic. The get varnish on them which makes them stick. You can spray carb cleaner on the front and back, but they have to come out to clean the sides and top. Usually clears up a stumble.

Shanman: To me, the hardest part of carb work, besides getting the carbs on and off, is removing the dozens of phillips-head screws without stripping the heads. Did you rejet to fix leanness from an exhaust change? Did rejetting make you bike run better?
hehe, thats so true about the dam phillips screws..i always replace them with allen head bolts whenever i take any carbs apart...i use to have tons of them around but a good cleaning of the garage got rid of that nice supply last summer...

like i said in the carbcleaner post, just be carefull when spraying carb cleaner on the slides so u dont hit the rubber diaphram, might even be easier to wet a clean cloth with carb cleaner and wipe the slides down like that...the plastic ones do suck, the gsxr's were metal if i can remember..

hope no one minds me digging up old posts and giving my 2 cents on things, sort of bored at work here....plus the riding season is comming up and time to start getting the bikes ready for the season, if you havnt already :thumbs:
 
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