Should I rejet???

Hey guys,

I am new to this site as this is only my third post and I have a question regarding rejetting my carburetors. I just recently bought an 85 Maxim X 700 and it is my first bike to own. I am doing a complete "bob" job on my own (I am not a mechanic but have worked on plenty of vehicles in the past). I took the mufflers off because they didn't coincide with the look of the bike that I wanted, so now I am running straight pipes (stock pipes with no mufflers) and I know that I have to rejet, or at least I have been told by many that I have to. So my question to you is what do I have to rejet to and what parts should I use? Thank you for any and all input as I am a newbie to the motorcycle world!!

 

what model bike is it?
your going to have to put bigger main jets in your carburetors.
then your going to want to get some ear plugs

 

You got an "X?"

That's a 20-valve water-cooled motor and it's high strung as heck right out of the box.

Quite honestly, and I'm not trying to pee in your cornflakes here, but making major mods to the intake and/or exhaust system on that bike puts you in a whole different league than the guys cutting up 8-valve "airhead" XJs.

The "X" motor is the same motor that was used in the FZ-series sportbikes, but in a Maxim frame. STOCK it's absolutely blindingly fast. All you're going to do is take it down a few notches.

You'll get more out of it in stock configuration. Maybe change the mufflers.

 

Welcome aboard txaggie44.

I totally understand your desire to make your X unique, but eliminating the mufflers isn't such a good idea on the Genesis engine. The need for some back-pressure from the exhaust is very important, as the 5-valve combustion chambers help the engine breath so well. Running the bike without the mufflers will just kill the low end power-band regardless of how much re-jetting you do.

If you don't like the stock mufflers, find some shorty's that suit you taste.

I hope you heed our advise, as we're just trying to keep you from setting yourself up for a lot of aggravation.

 

Hey guys,

I appreciate all of the input and I will definitely take that all into account. I appreciate it. I have an 85 Maxim "X" 700.

Honda-what do you mean that I will kill my "low-end powerband?" Also, what shorties would you recommend and where could I find them?

 

Well, the incoming fuel air mix will flow right through into the exhaust during the overlap phase of the cam timing at Top Dead Center. Also, during the power stroke, some of the combustion pressure (that forces the piston down) is lost before the piston reaches Bottom Dead Center. Hope I didn't get too technical?

On the mufflers, you can search around on E-Bay to see if you can find some you like. Anything aftermarket will need to have the correct inlet diameter or a reducer so it fits the stock collector. I've seen some XJer's use Harley mufflers. Not sure if that's something you'd be interested in looking into?

Here's one example of aftermarket mufflers:
http://xjbikes.com/Forums/viewtopic/t=4 ... flers.html

Do a search on this site to see what you come up with.

 

straight pipes as in 4 pipes or 4 pipes into a collector and 2 outlets?
makes a big difference

 

The only exhaust parts that I removed were the mufflers so to answer your question Polock, I believe 4 pipes into the collector with two outlets. Honda-I found some shortys on eBay for very good prices so I might go with those if I still need to

 

The main reasons I want to change the exhaust is because a) they just don't look right with the new look of my bike and b) I want to try and get a deeper sound out of the exhaust if that is possible. I am also installing pod filters, as my bike did not come with an air box. How will this affect my situation?

 

How will this affect your situation?

Answer: Adversely!

You are setting yourself up to deal with absolutely the worst case scenario of Tuning issues.
Pods are known to be a formidable challenge, ... alone.
Good luck with that.

Adding straight pipes just to increase the decibel level, ...
Well lets just say you ain't-in for a fun-time at camp.

You'll have to re-jet!
You'll have to re-jet.
Re-jet and re-jet until you can re-jet in your sleep.

Pods and Straight Pipes fosters "Re-jet regret."

What you think you are doing it not ... "Fine Tuning"
You are, in consensus, ... "De-Tuning"
You aren't just asking for trouble, ...
You're begging for it.

http://www.ebay.com/itm/1985-Yamaha-X70 ... d0&vxp=mtr

 

Sounds like you looked through the variety of choices for the mufflers, so any will help maintain a decent amount of back pressure.

You didn't mention anything about pods before? As RickCoMatic mentioned, that's another path you'll want to avoid going down. Get a stock airbox back on it, because the rubber tubes essentially are velocity stacks, and they help your bike perform its best with the Mikuni CV carbs.

There are quite a few discussions on that subject on this site. Here's a couple:

http://xjbikes.com/Forums/viewtopic/t=3 ... =pods.html

http://xjbikes.com/Forums/viewtopic/t=4 ... =pods.html

I have a much nicer X airbox available than the one Rick linked to that you can check out here:
http://xjbikes.com/Forums/viewtopic/p=3 ... tml#362403

Let me know if you're interested.

Tony

 

For a deep tone - go with a large diameter and some length,
just don't over do it

 

omg, that exhaust is so funny

 

You really should begin by restoring to stock, then Tuning to the Hairy Edge of Dialed-in.
Valves.
Spectacularly cleaned Carbs.
Pilot Mixture Screws removed for cleaning. A must.
Bores Cleaned, chased, Anti-seized
New O-rings.
Passages flushed. Especially Main Air. Requires removing Nozzles. Flushing Air Passage supplying Air to the tiny bleed orifices of the Emulsion Nozzle.
Welders Tip Cleaning Set or Guitar Stringing all 16 to 20 Air Supplying Orifices for Siphoning and ->Atomizing<- Main Jet Fuel. A must.


The ability to TWEAK these Air Screws is necessary for Fine Tuning, especially during future re-jetting experimentation. Experimentation.

Everyone who attempts to run Pods with Exhaust Mods too is a pioneer.
You might find a level of performance you can live with.
More importantly, you'll need to find a condition your Engine can live with because you'll need to evade any Critically LEAN condition.

These Bikes LOVE to run Lean, Tex!
You'll love it too.

But, ...
Air-cooled Aluminum can come to ruin if exposed to a Critically Lean condition generating temperatures above which Aluminum can't handle,
leading to disaster.

 

It's an "X" motor. Pods and open exhausts will simply kill the blinding performance it was once capable of. If you've never ridden it in stock trim, you'll probably never know the difference. You might be able to get it running halfway decent, but don't race a stocker.

That motor came from this bike:

 

Wow! Thank you guys for all of the wonderful advice. I just learned a lot of things that I didn't know before. Every part of my new Carburetors has been cleaned and cleaned some more already as you said rick. Since I do still have the collector on the bike and if I were to stick with getting shorties, would y'all happen to know what size jets I would have to get? How do I know how "lean" the bike is running?

 

Ultimately - you have to read the plugs, if you insist on a non-stock configuration. And as said before, you enter the realm of the "tuning nightmare" , but on an "X" - so most of us can't give you any accurate advise.
If you run too lean, you burn up your motor.
You need to replicate your intake and exhaust restrictions and flow dynamics - the best you can.
Anything else is screwing things up.