My 1999 Modified Blaster Case Study

[99LRDblaster]

I'm just going to lay this out there since I don't know what the issue is for sure, and I thought I would get other's two cents on the matter...I kind of know I'm going with a bigger carb, but might as well get some opinions from others.

WHAT:

1999 Yamaha Blaster
Mods:
-Trenga Racing/LRD Specialties Chrome Pipe and Blue Powdercoated Silencer
-Full MX/Trail Stage 3(PD#3) Port and Polish with rifled exhaust port from Hollywood Dirt Productions
-Milled head .30 and rechambered head
-Stock 26mm Mikuni carb bored and rifled to 30mm
-Vito's Needle
-Bored .050 over
-Wiseco Pro-Lite Forged Piston
-Boyesen Pro Series carbon fiber reeds on stock reed cage
-Uni Air Filter
-Outerwears Air Box Screen Cover
-Tag X5 Handlebars
-Scott Grips
-+3 swingarm
-Flipped front rims
-T.M. Designworks Oil Injection Block Off(runs on pre-mix)
-Nac's Racing Gripper Seat Cover
-Polished Throttle Cover
-Motion Pro Brake Cable
-AC Front Aluminum Bumper
-Front Works Dual Rate Shocks
-14 tooth front sprocket upgrade
-Rear Douglas .190 Polished Aluminum Rims
-20" Rear Maxxis Razr Tires
-19" Front ITP Holeshot Tires
-Shaved Front Fenders
-Blue Painted Wheel Hubs

Jetting:
Spot on all the way around. Jetted by myself, deep chocolate milk color at all ranges of the thottle through 4 plug chops. Jetting confirmed to be correct by a Yama tech and friend as well.

Problem:
Won't beat a stock 400ex in a straight line...despite hearing reports of numerous others with similar mods being able to do so.

Solution?
Well my hypothesis is that the carb...whilst bored up to 30mm....is still too small. HWD said the optimal set up would be with a Keihen 33mm, but a 30mm would work. Engine runs fine, compression is fine, jetting is fine......so it's about all I can bank on at this point. I'm open to suggestions though. I'm thinking in the next month or so, picking up a 33-35mm carb and just seeing how it fairs for sh*ts and giggles. What are some of the complications of putting a larger carb like that on? I know the intake boots are different, but I might be able to open up the stock boot and make a larger one fit in there. Kind of would like to retain the stock air box, but realize it might not be possible, so I might just get a clamp on and put on an outwears and make my own custom air box to shield it from debris during trail riding.

 

[sicivicdude]

What's your compression reading right now?

The trade-off for a 33-35 mm carburetor is less torque and a lower "hole shot". The upswing is more capacity for power output on the top end. You have the correct pipe for the job but your intake is lacking. Most people, once they get to your stage, ditch the stock aribox for something aftermarket and opt for the larger carburetor.

I'm not saying those two things are the magic bullet to solve your problem but they seem like the next logical step in freeing up HP's.

 

[little3mil]

its prolly your gearing is too short try a 38 or 39 in the rear then race him. i absolutely love my 33 pwk, great carb. your revs seem to be hanging a tad bit off the gas, may be pointing to a very samll airleak somewhere. have you done a leaktest?

 

[99LRDblaster]

What's your compression reading right now?

The trade-off for a 33-35 mm carburetor is less torque and a lower "hole shot". The upswing is more capacity for power output on the top end. You have the correct pipe for the job but your intake is lacking. Most people, once they get to your stage, ditch the stock aribox for something aftermarket and opt for the larger carburetor.

I'm not saying those two things are the magic bullet to solve your problem but they seem like the next logical step in freeing up HP's.

I'm fairly satisfied with the airbox setup right now. I don't mind running clamp ons, but I would build a box around a clamp on so it's basically just what I have now. I don't like running straight clamp ons because they get dirty easily, can be damaged by debris, and make air/fuel settings screwy since at low speeds you will run rich but at high speeds with all the air turbulence(and higher airflow passing through the filter membrane), it will run leaner. It's alright for drag setups, but inconsistent air/fuel mixtures bother me.

It's got more than enough torque. Compression is 146psi. I know how the larger carbs will effect performance, but I guess I just expected more from even a 30mm. I guess I am just curious what others are running for their aggressive port/carb setup and their results. I suppose that's where most of my curiosity lies.

 

[99LRDblaster]

its prolly your gearing is too short try a 38 or 39 in the rear then race him. i absolutely love my 33 pwk, great carb. your revs seem to be hanging a tad bit off the gas, may be pointing to a very samll airleak somewhere. have you done a leaktest?

I don't really need a faster top speed. I already have the 14tooth I'm pretty content with that setup as I mostly due trail riding, but we get out into open areas from time to time. The 33pwk was the suggested carb. I'm just wondering if 3mm more(3 friggen mm ) will help it out....I'm thinking so.

I did a leakdown last year and it was A-OK. I haven't ridden it in years, so when I go through with all this and pick up a larger used carb, I will be doing another one to check. I've noticed that it lingers as well a bit and I always play it safe with issues like that. I know the cylinder, head, and reeds are sealed tight....trust me on that one. I:I I'll check her out again regardless. I might post a riding vid sometime if the snow clears and take it out for a couple short bursts....can never get past 3rd though since I'm in the city. I might just take it out to my friends house out in the country and store it out while I prep it up some more. I'm kind of getting to the point of just keeping it instead of selling it since I've invested enough money in it as is and I could probably get $1500 at best out of it now.

 

[little3mil]

imo a 35mm would kill all your low end snap, i would run a 33mm if it were me. i run a FLOTEK aggressive trail port & custom machined head, vf3 reeds, +4 timing adv., power pros pipe, 33mm pwk, cfm airbox with uni pod filter, 14-39 gearing on av gas and i dont see a filter/pipe 400ex beating me ever, i beat my ladys modded raptor 350 by 5-6 lengths and its just about as fast as a piped turd00ex

 

[99LRDblaster]

imo a 35mm would kill all your low end snap, i would run a 33mm if it were me. i run a FLOTEK aggressive trail port & custom machined head, vf3 reeds, +4 timing adv., power pros pipe, 33mm pwk, cfm airbox with uni pod filter, 14-39 gearing on av gas and i dont see a filter/pipe 400ex beating me ever, i beat my ladys modded raptor 350 by 5-6 lengths and its just about as fast as a piped turd00ex

Her Raptor AKA Warrior must have quite a few mods. My neighbor had a piped warrior and I raced that, but that was just a joke of a race. I was so far ahead, that I basically just gave up.

Thanks, that's nice to see a setup similar to mine. I don't have the timing changed, but other than that, that's nice to hear. Yea, that's one thing I was wondering. I kind of figured if it was a 240, a 35mm would be good, but with the stock bore, it's probably a little too far out there even with the porting and head milling. I saw somebody had a 35mm for sale in the classifieds, and used 34mm 250R carbs are fairly plentiful, but I might hold off and wait till somebody has a used 33mm for sale. They seem to be semi difficult to find in classifieds though...guess there is always ebay though. How are replacement jets and all that jazz for the 33 PWK? What jetting setup are you running?

 

[little3mil]

well it has gears, pipe, filter, hd clutch and 19" tires so it goes pretty good for a 4 joke oh and she weighs about 55lbs lighter than me too...

 

[99LRDblaster]

well it has gears, pipe, filter, hd clutch and 19" tires so it goes pretty good for a 4 joke oh and she weighs about 55lbs lighter than me too...

power to weight ratio. I:I Works against me from all my weight lifting. I went up to 200lbs but I'm back down to 193. I'm only 5'7"

 

[little3mil]

My neighbor had a piped warrior and I raced that, but that was just a joke of a race. I was so far ahead, that I basically just gave up.

but you cant pull on a 400ex?

and yes weight is a major factor to any kind of racing

 

[Larry's Shee]

A stock carb can't be bored to a true 30mm because the slide isn't that big. It could be oval/tapered bored 30. Also try to find a local shop for jetting needs. As far as the race it could be the rider or may be time for new rears.

 

[99LRDblaster]

but you cant pull on a 400ex?

and yes weight is a major factor to any kind of racing

Nope. It was my friend's 400ex. He had a toomey piped blaster as well and we stayed decently close, but it was just a little faster in all places, low, through the gears, and top end. Bought the 400ex right off the floor so we know it was bone stock. He sold the blaster and 400ex and has a stock YFZ right now.

 

[99LRDblaster]

A stock carb can't be bored to a true 30mm because the slide isn't that big. It could be oval/tapered bored 30. Also try to find a local shop for jetting needs. As far as the race it could be the rider or may be time for new rears.

It's "rifled"(like on a gun barrel) but it is an circular bore. I've seen other shops bore it to 30mm, but it's the absolute max you can go with the stock 26mm Mikuni. I am better at jetting than most of our shops, but after it wasn't quite up to my standards, I kicked myself and shelled out the $$$ and took it to the Yama Tech at the shop and he didn't change anything because I had it spot on already.

When I raced the 400ex, we switched riders.....result was pretty much the exact same when I got on the 400ex and he got on my blaster.

 

[99LRDblaster]

and yes weight is a major factor to any kind of racing

Tell me about it. I'm a freak when it comes to power to weight when it comes down to anything....quads, cars, planes, football, you name it.