Need to rejet??

well you should get an aftermarket exhaust before you do those other mods. if you increase the air flow and fuel flow by porting, reeds, re jetting, and dont put an aftermarket exhaust then you will be restricting your bike alot. change your exhaust, reeds, air filter then rejet for those. then send your top end to ken oconnor for porting. he does an awesome job.

Anytime you change the airflow in or out of the motor, you should AT LEAST check the jetting to make sure there isn't a better jet to be using.

This includes changing anything in the intake tract, exhaust, cylinder (porting), head (rechambering), or crank (stroker).

You want to just do a plug chop to on the safe side.

As far as reeds go, go with something reasonably priced if you are going to get something for the stock reed block. Boyesen pro or power series reeds can be had for like $30. Vito's dual stage reeds can be had for a few bucks less. Both good choices.

The trick with reeds (which maintain the stock reed stop) isn't how much more flow they can attain, but how much faster they can open and close. Kind of like a reed spacer, they don't add power... only adjust it. Dual stage reeds will give you a little more throttle response.

Also, who are you getting to do the top end porting?

If he's well versed in porting then he should be able to custom tailor the duration numbers around your setup. Porting isn't rocket science (it's removing cylinder material to optimize the port size, shape, and height) but like I've head so many times before... "common sense ain't so common".

I've use the vito's dual stage carbon fiber reeds before and they performed reasonably well overall (money being no object) but I would rate them very good for the price.

A "plug chop" is running an engine with it's current fuel delivery configuration at a specified throttle position (plugs are USUALLY used for WOT to figure out the main jet size but can be done at any throttle position) for an short period of time with a brand new unsoiled spark plug installed followed immediately by an abrupt shutdown. You then "read" the color of the ceramic insulator around the electrode for coloration marks to determine if the jetting you are using is the proper jetting for the engine configuration.

http://www.blasterforum.com/engine-13/spark-plug-chop-20247/

The first link is dead (it decribes the process as I did above) but the second link is a pictorial of the expected spark plug insulator colors.

Once you've determined how the current jetting is running, you change it based on your plug chop findings and install a new spark plug to redo the "chop". Once you've got a nice coffee brown color at the base of the electrode, your jetting is perfect.

I have a blaster it was running lean I will be putting a new top boyesen reeds an lrd right bend racing exhaust and have it with no airbox lid which main jet size should I get?

Why was it running lean?air leak or jetting?this is a very old thread

It was running lean because the guy I bought it from used chainsaw oil and ran 50:1 so that caused my piston to crack because it over heated because it was running lean I didn’t know anything about that at that time so which size should I get with the mods I will be putting? So it was because of the jetting o and it would also leak either gas or oil a little bit tho

2strokedavid said:

It was running lean because the guy I bought it from used chainsaw oil and ran 50:1 so that caused my piston to crack because it over heated because it was running lean I didn’t know anything about that at that time so which size should I get with the mods I will be putting? So it was because of the jetting o and it would also leak either gas or oil a little bit tho

Click to expand...

Should have started your own thread, this one is eight years old

Oil mix ratio is lean on oil, not gas. Not saying it did or didn’t cause the failure, saw oil isn’t right for this use

Yeah I know that’s why I use yamalube now put either way I need to rejet because of the mods I will be doing so which size main jet should I get? Do you know if the Lrd exhaust is good?

BTW, don’t use cheap Chinese/Amazon/Egay parts.
OEM cylinder and Wisec is the proven way to go