Carb jets and temperature.

[sporty982000]

I recently as some of you may know picked up a 2001 stock blaster (blown for my step son). I already got the jug in the shop being bored. and it came with another frame and parts.


I found out, that my relatives son races with a 2005 blaster and aside from a recent top end rebuild. and a fmf fatty and core 2. he runs a jet size of 220.

He recently bought and tried the V3 reeds and while racing, they broke/ chipped and cracked. due to chatter.


Now, His mechanic, says to run 220 in 100 degree heat. So thats what hes been using during those temps while racing.

When I shared with him about 260 on up jets, he was a bit surprised to go that high up.

And his son is a good racer, wins allot of races or finished in the top 3, against racers running 4 cycles and against 18-20 year olds. So hes a good racer.

 

[joeak47]

You should jet the engine and go by plug readings. Do a plug chop,or aleast do it the old school way by looking at the insulator. Make sure its a mocha brown color.

 

[motoman159]

He may have a larger carb

 

[sporty982000]

The reply was not what I was looking for.

It was wanting to know about jets, what is recommended for differnt temperatures.

I trust his mechanic and his son has been racing for 5 years. with these set ups.

I know hwo to check the plug for color. that not what I was asking.

 

[motoman159]

The jet size deppends on your mods, always plug chop I think it's richer when hotter? And 220 Is lower than stock and if you have ANY mods you will blow it up (unless you live 1000 feet down In the ocean)

 

[sporty982000]

Thanks, much better reply, and I thought after I replied, I might have ben a bit rude. So I aplogize for that.

No here in illinois, and its a stock carb. We spent about 2 hours last night, sitting around talking blasters.

Thats what I had said to him, wow, you running a 220 and stock is 230. But hes been running that for a few years now,. and no engine failure or issues.

He bought it new in 2005 for his son and racing it since, and the first top end rebuild was only two months ago.

For me this is about learning, Im complexed on this also. on the 220 jet, fmf fatty anf core 2 pipe, other than that and the trying of the v force 3 reeds, which he ran into issues and found they wiggles and flapped to much and broke during the racing, the dips, jumps, destroyed them.

So, he has very little mods to it. compared to what I have read on here. he still runs the oil injection, no block off.

And runs bel ray 80 weight tranny oil, in the crankcase.

And there winning. I mean I told him, even what the fmf site, suggested for jets and extra with that pipe and silencer.

Trying to understand, why the mechanic said go with a 220, and the needle fyi is on the 3rd setting. i forgot to mention that.

 

[JBRoc01blaster]

This is a very interesting topic, jetting has been discussed on here a thousand times but its always talk of " your running lean " and " you need to bump up your main jet ". I also have heard from a guy that works at a parts shop that I shouldn't run over a 240 - 250 main and he knew I had a fmf gold series fatty, powercore 2, vforce 3's and holes in my air box lid. There was another younger guy there ( maybe 30 ) who said he's been racing for years and he trusts that guy with his bike and has had great success from taking his advice with mods and jetting. The kid I got my blaster from did all the mods minus the holes in the air box lid, he works on atv's at a machine shop fulltime and he said he never felt the carb needed a bigger main jet and he premixes at 40-1. My blaster is a 01 and I just had it bored .020 over in March which tells me that motor went over 10 years with the stock main and only 1 overbore. And when I blew my motor I wasn't checking compression and the skirt on my piston shattered so its possible it was on the original bore and the chunks of piston scuffed/gouged the cylinder deep enough that it required a bore of .020. Also when I rebuilt my motor I noticed the old spark plug had a PERFECT tan/light brown ring on the outside of the insulator.

 

[Blaaster]

The amount of oil in the premix can play a big part in this equasion.

32:1 is what most people on BF mix at, and jetting info is based on that.

So if you use 40:1 and you can decrease the jet size, because of more gas in the mix.

With an air temp of 100 deg, elevation and running oil injection, (where there is no oil in the gas to lean out a mix) one may just get away with smaller jetting.

The guy racing the #220 main may be looking for absolute top performance (at the expense of engine life) which you will get with a leaner than optimum jetting. He too has his needle on a richer setting than what is recommended for 100 deg air temp.

As to ones own bike, there are way too many variables to selecting the correct jets, do not just jet on what someone tells you, listen to their advice, then jet on the rich side and plug chop to correct to the desired jetting.

 

[sporty982000]

Some good replies. I like. I like.

See I think I was hoping to hear something like this. He was shocked when I mentioned jets at 260-300. And I wanted to make sure I mentioned what he had and ect.

Ya his new bore job was .020 or 66.50mm, after 7 years, this is not bad.

I just found out today, my sons,that is why I am hear now. his just needed bored .010 over and just bought the piston kit for it today, his is stock 2001. I mentioned it and shared pictures in the introduction section.

But I have a fmf fatty and corre 2 and another pipe and muffler. a dnf ? i think or something. and might put it on, but all the different jet settings and ect. has be concerned. were talking about a 12 year old, who is only gonna light ride it and not haul azz with it. So I picked up a wsw piston kit.

 

[Blaaster]

I would start at #270 for the FMF with the lid on.

If the other pipe is a DMC, they seem to be thirsty brutes, and with the lid on I would start at #290, with the needle clip on the richest setting.

Then plug chop to correct.

 

[Blaner]

@Sporty982000 : http://www.blasterforum.com/engine-...ressure-how-jet-accordingly-39872/#post524142