po

VintageMBike

Been Around the Block
Got an IMMACULATE 900F with only 9k miles.

Had an issue with the damn bike not going about 100mph. Its quick off the line, etc etc, but wouldnt go above 100.

I was going to rejet the carbs but something told me to check and replace the air filter first. Look at what the previous owner did. smh

Pic of the filter and my bike below:
 

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Re: 900F. Maybe THIS is the PROBLEM!! (Previous Owner Stuff)

The k&n filter makes my 750 run lean. That’s probably why they taped it up. I put a stock type paper filter in mine and it runs great


Sent from my iPhone using DO THE TON
 
Re: 900F. Maybe THIS is the PROBLEM!! (Previous Owner Stuff)

SquidHunter said:
The k&n filter makes my 750 run lean. That’s probably why they taped it up. I put a stock type paper filter in mine and it runs great


Sent from my iPhone using DO THE TON

well, due to emissions back then, these bikes were shipped lean from the factory. And yeah K&N's flow more air so the PO taped it up. Bad move though. I couldnt figure out for the life of my why the bike wouldnt go above 100 (restricted air it seems). I put the paper OEM in and will test top speed some time this week. Not only does that taping restrict the airflow, but it makes air intake uneven which is another problem. not smooth
 
Re: 900F. Maybe THIS is the PROBLEM!! (Previous Owner Stuff)

Nice looking bike !
 
Re: 900F. Maybe THIS is the PROBLEM!! (Previous Owner Stuff)

datadavid said:
Why not rejet accordingly?

By all accounts the bike doesnt need a rejet, esp on this model when going from 2 into 2 to a 4 into 1 which I have now.

The previous owner threw the K&N in there, probably realized it was getting too much air because the K&N flows more air, and then taped it off to reduce airflow.

I didnt tape that filter, the PO did and I discovered it and took it out.

Now that I have put the stock OEM filter in, everything *SEEMS* to be fine. The problem I had (with the old filter in there) is I couldnt get the bike over 100mph. Now its clear why. I expect that over the weekend, when I can take the bike out somewhere and speed and not get tickets, that it will go over 100 with the proper filter in.
 
Re: 900F. Maybe THIS is the PROBLEM!! (Previous Owner Stuff)

Yea but why dont you rejet for the k&n? Or is it one of those press-in no tamper deals?
 
Re: 900F. Maybe THIS is the PROBLEM!! (Previous Owner Stuff)

datadavid said:
Yea but why dont you rejet for the k&n? Or is it one of those press-in no tamper deals?

I have my own business and 3 kids. I have zero time and the Mrs. got fed up with me spending time in the garage while she was dealing with the kids.

SO i would have had no other choice than to pay a local mechanic who wanted like $400 (ugh) to do it.

So I took the path of least resistance, and just put the OEM air filter in. The problem was, I was speedy off the line, etc, but COULD NOT get above 100MPH. I found out why when I saw that taped K&N filter.

I did buy a TON of up and down jet sizes, but dont think I need them now.

I am going to put in a (rare) V&N race baffle that was out in the 80s when the bike came out. I want more noise.
 
Re: 900F. Maybe THIS is the PROBLEM!! (Previous Owner Stuff)

I can sure understand that! Then you have the wonders of time consuming rejetting ahead of you for me it usually takes years to get it 100%...
 
Re: 900F. Maybe THIS is the PROBLEM!! (Previous Owner Stuff)

datadavid said:
I can sure understand that! Then you have the wonders of time consuming rejetting ahead of you for me it usually takes years to get it 100%...

Dealt with this with my Yamaha. It took 45 minutes to jet that right. Its usually the Main jet that is the issue. My response from idle to 1/4 throttle is great. Not sure about 1/2 to full throttle with this new filter. Will try it over the weekend. That is, try to go above 100MPH
 
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