Jump to content

421 4mil longrod cub, NEED HELP


GrayRacing

Recommended Posts

ok, this is my 1st year on a cub. a guy i race with tells me that he just buys the cylinders with the ports already on them, and he runs 3.2s in 200ft. ok, i put mine together, and im running 3.4s....anyone have any suggestions of how everything needs setted up ? thanks if you do.

Link to comment
Share on other sites

like, what does my needles to be on, and the timing. i ran a stock 4mil last year, and set my timing on 7 degrees, and im not for sure about my needles. im running with power jets, and im too fat right now, i need to lean it up some. but im not for sure where everything needs to be. and btw, im 16, and weigh 150 pounds, and there is a guy that weighs way over 200 down there and he runs 3.2s, and hes from a track called isom.

Link to comment
Share on other sites

im running with a direct drive lockup, 17cc domes, and i have a good set of studded tires, but im going to 22 inch realtors. im also running wicked performance silent drag pipes and the packing is almost burned up in them, and alot of people are telling me that silent drag pipes suck, but they are all i have because i sold my CPI's. my cubs have the ports that they come with, but im going to send them off to K&T if i cant get it in the 3.2s

Link to comment
Share on other sites

lol. im trying to lose weight. but if i dont get the bike to run right, im just gonna send the cylinders off to k&t and let them port the heck out of them. and im running 36mm pjs btw, they are the best set of alky pjs in kentucky.

Link to comment
Share on other sites

If this is your first cub IMO you are wasting your money spending money on getting them ported.

Learn to tune with what you have first.

Even if they do a WORLD CLASS port job, in 200 foot you'll get a tenth or so.

 

Just because someone else runs a 3.2 doesn't mean you will.

 

Pipes are holding you back as well as 36PJs.

 

I'd have CPI or Shearers and 39PWKs.

 

That 4 mil cub on alky can handle those easy.

 

Here's the best suggestion I can tell you. Do ONE THING AT A TIME. And do it over, and over again.

Look at your slips, they don't lie. One day work on the carbs and getting a good reading on your plugs. The next time work on your gearing...the next day air pressure.

It's going to take 5-6 times at the track to get a good baseline tune...

 

I also think 17cc domes are too small for a 4 mil on alky if you're less than 1,000 foot in elevation. I'd shoot for 19 or 20cc domes.

What is your cranking compression, what is your Compression Ratio and your squish?

Link to comment
Share on other sites

well im not sure about my compression, but when i kick it, it just about throws me over the handle bars. im buying new carbs, and im trying to get rid of these pipes, but i cant find a set of stinger pipes anywhere. some people say the porting helps, some say it doesnt, but i have a friend, and A&S built his motor and hes running low 3.1s and its the same identical motor as mine. but we are gonna lean it out a little a weak and look around for some parts.

Link to comment
Share on other sites

A. Those are all things you should know.

B. That's what I'm talking about with compression.

 

Too much compression and the motor could be fighting itself at the top end...that could easily be a tenth there.

 

I can tell you from experience as a cub owner...cubs are laid out very well from the factory.

In 300 feet a great port job is 1-2 tenths at most. In 200 feet it's even less.

 

You simply can't compare the gains made by porting a stock cylinder to an aftermarket, they really are apples to oranges.

 

Just because he has the same motor, again...doesn't mean you'll run the same times.

Just because his is ported and yours isn't, doesn't mean porting will get you there.

 

As said....find out what is going on with your motor as far as compression, etc.

Learn to tune what you have...get the most out of your setup. Take notes, what made you faster, what made you slower.

 

NO one just bolts on parts and goes faster. You have to make it all work together!

Good luck!

Link to comment
Share on other sites

If this is your first cub IMO you are wasting your money spending money on getting them ported.

Learn to tune with what you have first.

Even if they do a WORLD CLASS port job, in 200 foot you'll get a tenth or so.

 

Just because someone else runs a 3.2 doesn't mean you will.

 

Pipes are holding you back as well as 36PJs.

 

I'd have CPI or Shearers and 39PWKs.

 

That 4 mil cub on alky can handle those easy.Here's the best suggestion I can tell you. Do ONE THING AT A TIME. And do it over, and over again.

Look at your slips, they don't lie. One day work on the carbs and getting a good reading on your plugs. The next time work on your gearing...the next day air pressure.

It's going to take 5-6 times at the track to get a good baseline tune...

 

I also think 17cc domes are too small for a 4 mil on alky if you're less than 1,000 foot in elevation. I'd shoot for 19 or 20cc domes.

What is your cranking compression, what is your Compression Ratio and your squish?

 

 

 

There's your answer^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Link to comment
Share on other sites

IMO...they'll be better than the 17cc.

You might lose a little out of the hole due to less compression, but you can bump your timing 1-2 degrees to compensate for that.

It'll rev out further.

 

I personally like domes cut for alky...but you gotta run what you have.

Link to comment
Share on other sites

well ok, im doing a little at a time, but i got a better set of tires, and my bike went from a 3.42 to a 3.302, i went to a set of studded realtors, but im going to a set of my smallbore grandrivers this week, and im gonna borrow a set of pwk 39s off my buddy to see how much more i gain.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...