Engine Running Too Hot?

[kamposs]

I recently purchased a 2003 Yamaha Blaster, stock. The top end was junk. I took off cylinder and it was scorched. I bought a replacement cylinder and rebuilt it. It started right up, but only ran on choke. It had some no name aftermarket carb, so I bought TORs removal, mikuni replacement carb, and oil block off kit. Put all three on, ran 32:1, and it starts, idles, and runs like every other two stroke I have had.

Figured I would check the spark plug before putting it back together, and noticed it was gray:


I've never seen this before, so I looked it up, and from what I read it is running too hot. Which could be a result of high compression, running too lean, or/and advanced timing. The compression is fine, it smokes just as much as any other atv I've had, and idles good as well. It has the stock timing plate on which is non adjustable.

I am stumped. Runs fine, just don't want to ruin another cylinder on it. Could use some help, thanks.

 

[Awk08]

what model and size carb ?
what jetting is in the carb you bought ?
Pilot, main, needle #'s ? and needle clip setting ?
oil injection port blocked off on the carb ?

has it been leakdown tested for any airleaks ?
airleaks = lean = hot = fried
common areas for leaks are the intake, head and base gaskets, and crank seals.


The plug color your looking at was deposited by all jetting ranges, which doesn't tell you which one is depositing what color.
a proper plug chop is the best way to confirm main jetting ....
https://www.blasterforum.com/threads/how-to-plug-chop.53237/

 

[kamposs]

this is the carburetor i bought:

https://www.ebay.com/itm/Carburetor...e=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649

"Mikuni 28mm VM24" - is what it says. The problem is that the jets do not have number on them. I bought the proper sizes "230, 32.5, etc", for the stock carb, but they do not screw into this one. So just ran it as is.

I have done plug chops in the past, but they are not easy to do where I live "city area".

 

[Awk08]

There is your problem >>>>> "I bought the proper sizes "230, 32.5, etc", for the stock carb, but they do not screw into this one. So just ran it as is."

the chances of any aftermarket carb having the correct jets for a blaster ....... you've got a better chance of hitting the lottery
I suggest you find a used stock carb from another blaster and get the correct jets back in it before it fries

 

[Awk08]

BTW ..... your link to the carb doesn't work ?

 

[kamposs]

does this url work? https://www.amazon.com/dp/B01F4QPBV2/?tag=jyj356j5-20

I may just end up getting drill bits for the correct jets I bought and drilling the ones in the replacement carb to match.

 

[Awk08]

does this url work? https://www.amazon.com/dp/B01F4QPBV2/?tag=jyj356j5-20

I may just end up getting drill bits for the correct jets I bought and drilling the ones in the replacement carb to match.

yes that link worked.
that carb is listed for 4 strokes of 140-160 cc
were running 195cc 2 strokes, guaranteed those jets aren't correct.
I wouldn't run that chi-wanese knockoff carb