PLEASE HELP ME!!!!!!!

[Yz125killer]

I just picked up a 2000 blaster on trade for a AR-15 and it's a pile of crap. The engine is brand new bottom end to top,I was shown all paperwork and pictures of the build being done October '23.

Afterwards it sat til now and just went to crap. I have read all the forums and ran through the list as follows,
Compression 110psi
Leak down, passed
Wood riff key good
Spark plug, changed BR8ES
Carb, new (Vito's performance 26mm)
Reeds, was vforce, back to new OEM
Ignition coil, new OEM
TORS delete,wires tied together
Park break was already gone and no wires
Oil mixer gone,premix 32:1
FMF fatty exhaust
Power core silencer

Haven't checked my jet size yet, haven't calibrated my float height either.

ISSUES.
starts right up,idles wonderful,runs great about 1/2 throttle. Anything after half throttle spits,sputters,bogs and backfires.
If I pull the choke it runs like a ape but dies if I'm not all in it.
I did the air box lid test,way worse.

I'm ordering a set of calipers and the float measuring tool tomorrow.

What am I missing here. The thing just don't want to act right,I even got so mad that I threw it in the shop,took pictures of it and told my son I was selling that POS.
I just had to calm down,create a profile on here and let you guys help me save this machine.
Anyone please give advice and tell me what I'm missing. Feel free to also text me or email me directly so I can get it figured out.

9727865122.
chrisbarnes619@gmail.com

 

[RIDE-RED350r]

Welcome aboard

So first off, you say turning the choke on helped it. That's a sure sign it needs more fuel, running lean. The air box lid test, if that means you removed it and it got worse, that definitely agrees with what turning on the choke told you.

I like Vito's, but I'm pretty certain all the carbs they offer for the Blaster are Chinese imitations of Keihin PWK carbs. Some have reported good results, others not so much. Anything can throw it off, jet sizes may or may not be consistent with genuine carbs, I've even seen main jet emulsion tubes with less and smaller holes in the stem.

But the symptom you are describing sounds like your main jet circuit is too lean. I would start by getting an assortment of jets and then begin dialing things in starting with the main jet and working your way down from there to needle adjustment and then pilot jet and idle air screw. If it proves impossible to jet, doesn't respond consistently and predictably to jetting changes, you may be on the right track to suspect float height. It may be a good idea to remove the carb, pull the bowl, and verify float height is correct before starting in with jetting adjustments. Improper fuel level in the bowl, wether it be too high or too low will give you fits.

 

[Yz125killer]

Welcome aboard

So first off, you say turning the choke on helped it. That's a sure sign it needs more fuel, running lean. The air box lid test, if that means you removed it and it got worse, that definitely agrees with what turning on the choke told you.

I like Vito's, but I'm pretty certain all the carbs they offer for the Blaster are Chinese imitations of Keihin PWK carbs. Some have reported good results, others not so much. Anything can throw it off, jet sizes may or may not be consistent with genuine carbs, I've even seen main jet emulsion tubes with less and smaller holes in the stem.

But the symptom you are describing sounds like your main jet circuit is too lean. I would start by getting an assortment of jets and then begin dialing things in starting with the main jet and working your way down from there to needle adjustment and then pilot jet and idle air screw. If it proves impossible to jet, doesn't respond consistently and predictably to jetting changes, you may be on the right track to suspect float height. It may be a good idea to remove the carb, pull the bowl, and verify float height is correct before starting in with jetting adjustments. Improper fuel level in the bowl, wether it be too high or too low will give you fits.

First off thank you very much for your input and welcome me to The forum. As I was expecting I figured someone would say something about the jetting and or the float height so I've already ordered a float tool and it should be here Wednesday or Thursday, do you know the OEM specifications for float height, and do you have a good recommendation on where to get jets, every time I Google it the first thing that pops up is Amazon Chinesem and I'm not sure the correct jet kit to get. I would really love to get this thing dialed in because I had one when I was a kid and I remember it was fun.

This thing just baffles me, I have a 450 4 stroke a YZ 125 and a KTM 125 and have zero issues out of them when it comes to tuning and running like monsters but these blasters are so tedious

 

[RIDE-RED350r]

I'm happy to help where I can.

As to the correct jets, we need to figure out exactly what carb you have from Vitos. I'm almost sure, but not sure enough to say they are all Keihin PWK clones. If you could send a few pics of the carb and then measure the ID of the engine side of the carb bore, that would get us on the path to knowing what jets you need.


As to where I get my jets, I only buy and use genuine Keihin jets and needles in my carbs. Jetsrus.com is a very good source, as is PJ Motorsports.com. I'd have to check them both, but Im pretty sure at least one of those websites has all of the specs for every Keihin carb currently in production including float height. The nice thing about newer Keihin carbs is the main jets are the same for most of them. But there can be some little differences in pilot jets. If you have a Vito's PWK clone, you won't have any trouble finding genuine jets for your carb.

 

[Yz125killer]

I'm happy to help where I can.

As to the correct jets, we need to figure out exactly what carb you have from Vitos. I'm almost sure, but not sure enough to say they are all Keihin PWK clones. If you could send a few pics of the carb and then measure the ID of the engine side of the carb bore, that would get us on the path to knowing what jets you need.


As to where I get my jets, I only buy and use genuine Keihin jets and needles in my carbs. Jetsrus.com is a very good source, as is PJ Motorsports.com. I'd have to check them both, but Im pretty sure at least one of those websites has all of the specs for every Keihin carb currently in production including float height. The nice thing about newer Keihin carbs is the main jets are the same for most of them. But there can be some little differences in pilot jets. If you have a Vito's PWK clone, you won't have any trouble finding genuine jets for your carb.

Okay awesome thank you so much I will keep in touch with you, of course it's the weekday so I'm currently at work but if I get home early one of these afternoons I will pull off the carb take some photos and some ID measurements and get those over to you.

 

[RIDE-RED350r]

Sounds good. I work days as well but also have alot of projects going on at home. But I still swing in here a couple times a day and see what's new

 

[Yz125killer]

Ok so I got the float tool which I will get around too in the next few days. I also got the calipers. I will be attaching all the photos of the carb. I took pictures of all sides and stamping in the carb for you.
It appears that it has a 190 main jet and the emulsion tube says 332 then a symbol then 0-0.
The intake (motor side) shows 27.79mm and the air intake side is 39.68mm.
OH AND A SIDE NOTE I GOOGLED MY ALTITUDE IS 509 FT. Just figured I would throw that in there because I seen a lot of people talking about their altitude.
I'm going to have to send more pictures separately apparently it only does 12 files!!!!

 

[Yz125killer]

Here are the other photos of the carb body. Sorry for such long messages and so many photos I just really want to get this thing figured out.

 

[RIDE-RED350r]

Well, what you have is a Mikuni 28mm round slide carb. Wether it's a genuine Mikuni or not will be tricked to find out as the Chinese copies are getting harder and harder to discern from the real McCoy.

I'm most familiar with Keihin carbs, I've been running them since the 1990s with some Mikuni sprinkled in on things like sleds. That said, I'm not as familiar with Mikunis jetting numbers. I see your main is a 190, in a Keihin that's huge, but I believe that's pretty small in Mikunis numbering system. I'm going to look on Vito's website and see whats what with the Mikuni 28mm carb they sell. From there we should be able to start making heads or tails of your jetting. If in fact that main is very small, that definitely agrees with what you found about putting the choke on helping it run better. But just in cruising around here on the forum, I seem to remember seeing main jet sizes in the low 300s for stock 26mm Blaster carbs. But, I know Mikuni does have a couple different types of jets for different carb models.


We will figure this out

 

[RIDE-RED350r]

I believe what you have is a Mikuni VM28.

If I'm right, these are the main jets that Jetsrus offers. You can check the dimensions listed on this link against the dimensions of your main jet.

If they match, I would order an assortment of mains starting with about 210 and ending at about 300. It sucks how expensive the little buggers are, but OEM jets are always the best option for quality and guarantee of being accurately sized. And once you have them, you have them.

Genuine mikuni hex jets 4/042 - Jets R Us

 

[Yz125killer]

Awesome, I appreciate your help very much thus far. I do agree with you by reading through the forum that I've seen Jets running from 230 upwards of 330 can I was cruising through their website last night about 10:00 laying in bed and yes those little suckers are pricey but compared to the price of a mechanic or something along those lines jetting the car is a lot better LOL. I will definitely get some Jets in my cart and Thursday when I get paid I will get them on their way. In the meantime I will go ahead and get my floats adjusted to somewhat of a stock height and throw in a new spark plug because I have like four or five new ones.

What do you think about the emulsion tube, I haven't seen very much talk about those or the numbers on them.

And FYI sorry if any of my messages ever come through kind of illiterate I use my Google speech to text on my phone instead of typing all of this and sometimes it messes up what I'm saying.

 

[RIDE-RED350r]

I don't know that I would worry too much about the emulsion tube unless we know for sure that your carb is a Chinese clone and it refuses to jet in.

I think one step at a time will be the winning course of action. Set your float to spec and then I would replace that 190 main with one about 3 sizes richer than stock spec for a stock Blaster. It will need a little more fuel with the larger bore carb but it won't be a huge increase.

 

[RIDE-RED350r]

Ok, so according to my Yamaha Blaster service manual, stock main jet size is 230. I would probably start at least three sizes richer than 230, which according to the chart I linked, should be a 260. For an assortment of main jets, I would probably get 220 through appx 270. This should be enough range to cover most any reasonable situation you encounter as well as the addition of most bolt-on mods. But I'm all honesty, you wouldn't regret getting as wide an assortment of main jets as you feel comfortable spending the money on. I wouldn't go much leaner than a 210 or 220, but expanding on the rich end, you will never regret having on hand. A small two-sided Plano style tackle box makes a great kit box for jets and other small carb parts.

 

[RIDE-RED350r]

I tried looking for that carb on Vito's website and wasn't able to find it. All I could find are Keihin PWK clones.

 

[Yz125killer]

I have wonderful news I stopped after work and bought a 230 240 and 250 and then set my floats to 21 mm as specified and she is running like a monster. Thank you so much for all of your help I honestly could not be happier.

But now I'm on to the next problem I just did new brake shoes on the front and they are working wonderful and you probably already see where this is going. I cannot get these rear brakes to work no matter what I'll attach pictures and see if you have any insight everything I read says to do an upgraded caliper kit with hydraulic brakes. What's your opinion any advice?????

 

[RIDE-RED350r]

Glad to hear the jetting changes got it sorted out? .

And it's a good thing too, while an engine that's running rich will never suffer any serious harm, running too lean can lead to damage ranging from premature piston and cylinder wear to complete piston/cylinder failure depending how what degree of too lean it's running.


As to the rear brakes, my daughters Blaster is the first that's ever lived in my garage and it had an MCP hydraulic rear brake conversion already on it when we got the machine. Unfortunately I can't give you any tips with the OEM rear brake as I have zero experience with it. There is a service manual download available on this forum. I'd suggest downloading that and seeing if it can shed some light for you.

What year is your Blaster?? Looks to be 1990s by the color scheme. Ours is a '95. Those colors from the 90s are pretty wild

 

[Yz125killer]

Supposed to be a 2000 with the upgraded purple plastics for the guys daughter but I have no paperwork or anything so your guess is as good as mine to if he was being truthful.