bogs out at full throttle

[Justin Moore]

Hi everyone,
I am new to this site and I am looking for help. I recently got a Yamaha blaster for my son. she starts on the first kick and idles fine, she drive at low rpms fine but once I go to full throttle she bogs down like something is holding it back and she was spitting out oil where the exhaust meets the engine. I drained the tank and put fresh gas and oil mixture using amsoil. I did a new spark plug, new air filter, new crank seal and crank cover gasket. I have totally ripped apart the carb and cleaned her out and after all that she got a little better but not 100%. I started to mess with the electrical stuff like the wire connectors coming from the stator because they were bad and also took off the cdi box and dried it out in the oven because someone said that it may be moist inside and I also changed the connectors on that and still doing the same thing. I am sure its something simple and stupid that I am over looking but I am new to the blaster I have a warrior so not sure what to do at this point other than change the stator and the cdi box to see if that will do it. Pleas help as my son is dying to ride this thing.

 

[Larry's Shee]

First off I would NOT take any more advice from that person ! I highly doubt that the CDI is designed for that high of temps. They are pretty much a go/no go item. If it got moisture in it it probably would not work at all.

Did you leak down test after crank seal? Did you replace both seals? Is air filter clean? Could you see light through the jets?

What year is it? Front drum brakes or disc? Is the TORS still hooked up? If pre 03-06 unhook 3wire box under hood. This a VERY common problem with all Blasters.

List any modifications that you know of. Lid/snorkle on air box? stock air cleaner? pipe? Main jet number?

I would try the TORS elimination first. 03-06 you have to cut/slice a wire at CDI.

Shot gun parts replacement rarely goes good.

 

[Awk08]

I'll add to larry's list .....

float level correct ?
https://www.blasterforum.com/threads/float-heights-and-how-to-adjust-them.50565/

brass washer under the main jet ?

and again ...
what pipe is on it ? and what size main jet is in it ?
an aftermerket pipe, air filter, air box lid off, all require a larger main jetting, the jet number is stamped into the side of the main jet, should be a 230 for a stock pipe/filter/lid on

 

[Justin Moore]

First off I would NOT take any more advice from that person ! I highly doubt that the CDI is designed for that high of temps. They are pretty much a go/no go item. If it got moisture in it it probably would not work at all.

Did you leak down test after crank seal? Did you replace both seals? Is air filter clean? Could you see light through the jets?

What year is it? Front drum brakes or disc? Is the TORS still hooked up? If pre 03-06 unhook 3wire box under hood. This a VERY common problem with all Blasters.

List any modifications that you know of. Lid/snorkle on air box? stock air cleaner? pipe? Main jet number?

I would try the TORS elimination first. 03-06 you have to cut/slice a wire at CDI.

Shot gun parts replacement rarely goes good.

Thanks for the info so I am not sure of the year as the person I got it from didn't even know what year it was. It does have drum brakes all the way around so its gotta be in the 90's or early 2000 because 2003 is when they made the changes. I did a pressure test with 10lbs of pressure and it held. I sprayed the engine down with soapy water also to see if anything would bubble up but I saw nothing. It has an aftermarket carb that says makuni which I was told was a good carb but not sure I cant tell the size of the main jet because I couldn't make out the number on it. It has a fmf fatty pipe with the stock muffler on it . It doesn't have the air box lid and the air filter is brand new uni filter hasn't even been in any dirt because it hasn't ben on the trails due to how its running. I didn't change both crank seals I only did the one on the clutch side where kick start is. Maybe I should buy new jets for the carb and see what that does.

 

[Justin Moore]

I'll add to larry's list .....

float level correct ?
https://www.blasterforum.com/threads/float-heights-and-how-to-adjust-them.50565/

brass washer under the main jet ?

and again ...
what pipe is on it ? and what size main jet is in it ?
an aftermerket pipe, air filter, air box lid off, all require a larger main jetting, the jet number is stamped into the side of the main jet, should be a 230 for a stock pipe/filter/lid on

Thanks Bro!! Not sure if you could see my response to larry as I am new to this site and don't know how it works when you replay. but it has an fmf fatty pipe with stock muffler. not sure of the year because the guy I got it from didn't know what year it was but it has drum breaks . aftermarket carb that says mikuni so it doesn't have the tors set up . don't know what size the main jet was because I couldn't see the numbers so not sure what size is in there now and it doesn't have the air box lid but the air filter is brand new uni. I think I may just buy new jets for the carb but not sure what size I should get with the exhaust and air box set up?

 

[Awk08]

I cant tell the size of the main jet because I couldn't make out the number on it

this is a recipe for disaster

aftermarket carb that says mikuni so it doesn't have the tors set up

some pics of this carb, and/or an inside measurement in MM's of the engine side to determine the size would help us help you.
a stock carb can have a regular carb cap if a TORS delete kit was used.
does it have an idle screw added to the side of the carb ? (a must for TORS delete on stock carb)

the jetting info below is for a stock VM 26mm mikuni, and may be close for a 28mm also.
if it's larger, the info below may not be correct, and possibly different physical size jets ?
I'd suggest finding a stock VM 26mm carb, your mods do not require anything larger and the jetting info here is scarce for larger mikunis.

I think I may just buy new jets for the carb but not sure what size I should get with the exhaust and air box set up?

I'd buy 270 thru 310 genuine mikuni main jets, start large and plug chop down

jets: read the description about messaging them what sizes you want, and adjust the quantity to how many you want
5 - (270/280/290/300/310)
https://www.ebay.com/itm/MIKUNI-HEX...Parts_Accessories&hash=item2311067205&vxp=mtr

get a pack of B8ES plugs for the plug chops too
4 pack, 6 would be safer......
https://www.ebay.com/itm/4-pc-4-x-N...303544?hash=item4648282e38:g:5BYAAOSw5BpdK-2g

plug chops: https://www.blasterforum.com/threads/how-to-plug-chop.53237/

 

[Justin Moore]

 

[Justin Moore]

This is the one pic that I have for now . I will be working on it this weekend so I will take more photos of the jets . I really appreciate all the help. A question I have is that someone told me because I don't have the air box cover on it that I am taking in too much air and that could be causing the problem. A friend of mine has a blaster with a full aftermarket exhaust and he said he didn't have to change his jets that they are still stock? what do you use to chop the spark plug?

 

[Larry's Shee]

Bad info from your friends. Just removing the lid calls for one size larger main. Better filter, another. Look on FMF site, it calls for FOUR sizes larger with their pipe, with stock filter, no snorkel, IIRC

Go to engine forum, carb sub-forum and look at “What jets are you using”

 

[Justin Moore]

Bad info from your friends. Just removing the lid calls for one size larger main. Better filter, another. Look on FMF site, it calls for FOUR sizes larger with their pipe, with stock filter, no snorkel, IIRC

Go to engine forum, carb sub-forum and look at “What jets are you using”

Thanks so much I will def check it out. It gets so confusing because everyone tells you o its not this try this lol I had a feeling that it could be the jets. I'm Just trying to learn the quad so that I can properly maintain it. I will keep you posted. Gonna grab some jets next week once I find out the size it calls for

 

[Justin Moore]

Thanks so much I will def check it out. It gets so confusing because everyone tells you o its not this try this lol I had a feeling that it could be the jets. I'm Just trying to learn the quad so that I can properly maintain it. I will keep you posted. Gonna grab some jets next week once I find out the size it calls for

ok So I just got off the phone with my local shop to see if they carry jets for a mikuni carb and he told me that my silencer is the problem not the jets???? he said I would need to get a silencer that matches the fatty pipe?? I think hes just trying to make a sale because I thought That I could leave it the way it is and just jet it.

 

[Awk08]

ok So I just got off the phone with my local shop to see if they carry jets for a mikuni carb and he told me that my silencer is the problem not the jets???? he said I would need to get a silencer that matches the fatty pipe?? I think hes just trying to make a sale because I thought That I could leave it the way it is and just jet it.

Lose that shops number ....Idiots !
Every change to flow into or out of the engine requires a jetting change.
the silencer is just that, it reduces noise levels, not change or limit exhaust flow out.

as for the pic of your carb, it looks like a chinese knock off, the airscrew is on the opposite side than a stock carb, with who knows what pilot, slide and needle in it ? besides what main jets to use ?
my suggestion is to find a stock carb, and we'll have you jetted and white knuckle riding with a quickness.
continue to roll the dice with that carb and you may need Ken Oconnor Racings # for a rebuild

 

[Justin Moore]

Lose that shops number ....Idiots !
Every change to flow into or out of the engine requires a jetting change.
the silencer is just that, it reduces noise levels, not change or limit exhaust flow out.

as for the pic of your carb, it looks like a chinese knock off, the airscrew is on the opposite side than a stock carb, with who knows what pilot, slide and needle in it ? besides what main jets to use ?
my suggestion is to find a stock carb, and we'll have you jetted and white knuckle riding with a quickness.
continue to roll the dice with that carb and you may need Ken Oconnor Racings # for a rebuild

Thanks Bro!! does the stock car come with the tors on it?? And do you have any recommendations where I can find an original carb that's not so expensive. Money is tight right now. My son is dying to ride and my wife is on my back about this thing LOL and how much time and money im putting into it but for the price I got it for I couldn't pass up plus I heard they were cheap to fix. I also want to say thank you for al the advice so far!!!!!! you and Larry have been so helpfull

 

[Larry's Shee]

You have inexpensive and you have cheep Ching Chong
Lots of difference

 

[Larry's Shee]

What was wrong with original carb? Start checking what and CL maybe put wanted on here and CL

 

[Justin Moore]

What was wrong with original carb? Start checking what and CL maybe put wanted on here and CL

I don't have the original carb. it came with that one so im not sure if I can just replace the jets in it and it will be fine or if I should get something else

 

[Larry's Shee]

Look in jetting section for setup like yours buy those jets, genuine Mikuni ONLY
If they don’t fit, at least you’ll have the right ones if you get stock carb.
Also search as to which dirt bike carbs will fit easily

 

[Justin Moore]

this is a recipe for disaster





some pics of this carb, and/or an inside measurement in MM's of the engine side to determine the size would help us help you.
a stock carb can have a regular carb cap if a TORS delete kit was used.
does it have an idle screw added to the side of the carb ? (a must for TORS delete on stock carb)

the jetting info below is for a stock VM 26mm mikuni, and may be close for a 28mm also.
if it's larger, the info below may not be correct, and possibly different physical size jets ?
I'd suggest finding a stock VM 26mm carb, your mods do not require anything larger and the jetting info here is scarce for larger mikunis.




I'd buy 270 thru 310 genuine mikuni main jets, start large and plug chop down

jets: read the description about messaging them what sizes you want, and adjust the quantity to how many you want
5 - (270/280/290/300/310)
https://www.ebay.com/itm/MIKUNI-HEX...Parts_Accessories&hash=item2311067205&vxp=mtr

get a pack of B8ES plugs for the plug chops too
4 pack, 6 would be safer......
https://www.ebay.com/itm/4-pc-4-x-N...303544?hash=item4648282e38:g:5BYAAOSw5BpdK-2g

plug chops: https://www.blasterforum.com/threads/how-to-plug-chop.53237/

which pilot jets do I Get. I know you said the main jet is hex but trying to figure out the pilot jet? FMF says I should have a 260 main jet, 23.5 pilot jet needle position on 3rd and air screw at 1.5. Does that Sound good?

 

[Awk08]

which pilot jets do I Get. I know you said the main jet is hex but trying to figure out the pilot jet? FMF says I should have a 260 main jet, 23.5 pilot jet needle position on 3rd and air screw at 1.5. Does that Sound good?

32.5 pilot, if FMF said 23.5 it is a misprint
the main .... their 260 suggestion sounds lean, 270 - 310 is what we've seen here
the stock 32.5 pilot has worked on every blaster I've worked on from stock to fully modded stock cylinders

 

[Justin Moore]

32.5 pilot, if FMF said 23.5 it is a misprint
the main .... their 260 suggestion sounds lean, 270 - 310 is what we've seen here
the stock 32.5 pilot has worked on every blaster I've worked on from stock to fully modded stock cylinders

ok so I changed the jets and the needle setting and put everything to the way FMF said and it didn't do anything I also did a new cdi box. At this point I am done with this quad. I don't know what to do anymore