Thumper Racing Big Bore Installed

I recently bought the big bore kit from Thumper Racing and
installed it on my X. Travis at TR was incredibly helpful before and after my
purchase. Here is how it went.

To work on this engine, you need to remove it from the bike. The Service Manual
documents the procedure, but doesn’t tell you when to stop – they assume you
want to take everything apart. Start with the plastics, tank, exhaust,
radiator, shifter, countersprocket, and brake pedal. Then, just disconnect
every wire and hose attached to the engine. You can leave the engine bolted to
its cradle, but you will need to temporarily pull the swingarm pivot bolt. The
fuel injector stays on the bike, as well as the mount for the fusebox etc.

Once the engine is out, it’s pretty simple to pull the head,
cams and cylinder. Just make sure you mark the position of the cams relative to
the timing chain, and make sure you wire the chain to something so it doesn’t
drop down into the bottom of the engine. I put everything into little plastic
boxes, stuffed rags into every available hole, and covered it all over while
the cylinder went off to be reborn.

Thumper Racing will fit the new sleeve into your cylinder. Now it’s just the
waiting which is about as easy as waiting for Christmas when you’re eight years
old. While that was going on, here is what else I did to the bike:

FMF Q4 Silencer with Powerbomb Header
K&N Air Filter
All Black Plastics
AIS Removal Kit
EXUP Eliminator Plug
Galfer SS brake lines front and rear
GYTR fatbar Clamps
Renthal Fatbar RC Mini Bend
Probend Composite Handguards
Enduro Engineering Front and Rear Axle Sliders
Symtec Heated Grips with Heattroller
Zeta Throttle Tube
Zeta Clutch and Brake 3-finger unbreakable levers
Flash2Pass Garage Door opener
Panasonic Relay and fuses from Eastern Beaver
Zumo power cable and mount
Yamaha engine guards from R model - painted black
Shift Lever from Driven Racing
Battery Tender Pigtail
Evotech Skid Plate

I know, it’s an insane amount of stuff. I have two other
WR250Rs (wife and daughter) so I console myself with the idea that a lot of the
stuff I took off can be used as spares for the other bikes.

I haven’t taken any pictures yet because I’m waiting for
parts on some of the black plastic. Specifically, I’m talking about all the
rubber pads, foam isolators, rub strips, heat guards, etc. The plastic comes
naked, and all that stuff needs to be ordered from an OEM source.

The kit from TR showed up on a timely basis. I probably
should have taken pictures, but when I have parts in front of me, I go into an
assembly frenzy. Pictures don’t take themselves. What you get is the original
cylinder, all cleaned up with a new bore, a new piston with rings, a set of
gaskets and the FMF controller.

Having never pulled a cylinder before, I enlisted my friend
Pat who has far more experience. We had spent about five hours pulling the
engine, and were about to spend five more putting it back on. Not too bad.

The piston went on easily enough. I had a question about the
rings, because it wasn’t immediately obvious what was top and bottom. A quick
call to Travis resolved that. After I pulled out the magnifying glass, I could
see the markings on the top of the rings. We also consulted the service manual
to set the gaps in the rings at their proper positions.

Slipping the cylinder over the rings was probably the
hardest part of the job. I was glad to have two people. We used Yamabond 4 on
the gaskets, being careful to restrict it to the mating surfaces. We were also
quite careful to torque to proper specs and in the proper order.

I had heard that the timing chain tensioner is difficult to
“pre-load.” I worked out a procedure which had it done in about three minutes.
Sweet.

After that, it’s just a matter of putting everything back
where it came from, less the EXUP and AIS which inexplicably are still in my
parts bin. Add oil and radiator fluid, and push the button.

It’s unnerving to take a fully functioning motorcycle and
turn it into a basket of parts. It is incredibly gratifying when you push the
button and it fires to life immediately. I ran it briefly then grabbed the instructions
for the FMF, which is easy to set. Travis provided the correct settings for my
pipe.

So how does it run? I’ve ridden the bike half a dozen times
and it feels … perfect. It’s literally hard to believe. (And I literally mean
literally, not the current common usage which means not literally.) Every time
I get off the bike, I think, “Is it really that good?” Then I get back on and
realize, “Yes, it’s that damn good.”

The bike has stock gearing, and now it pulls hard in every
one. The fuel injection seems spot on. Only occasionally do I get a mild pop on
deceleration.

If you’ve ever ridden an X, you know how nimble it is. Now
imagine it to be effortless. Balanced, and eager. Of course I still need to
change gears more than my Tiger 1050. But for anything under freeway speeds,
the X-bike will be my weapon of choice.

What’s next? I’m talking to James Renazco about a seat. And
I’m waiting on the tail light from Forest over at Wheeler. Maybe a Sidewinder chain set up after I’m sure of the gearing. Oh, and I’ll be glad to answer any questions.

Does it now have enough low end chug to keep you from having to downshift when in sixth with a stiff head wind?? Marc B

Great wright up, can not wait for my big bore kit one day

28marcb wrote:

Does it now have enough low end chug to keep you from having to downshift when in sixth with a stiff head wind?? Marc B

I haven't been able to find a stiff headwind, so I can't say I've done it, but I think the answer will be yes. With stock gearing you don't even hit 6th gear until 65 or so (indicated). That's one of many things I like about this bike. The gearing is truly wide. On my DRZ, I keep looking for a 6th gear. On this bike, I hardly need it.

I thought about the DRZ motard, but one thing you can't change is the transmission. I knew the X-bike would be down on power, but with the Thumper Racing kit, it's right back up near a stock DRZ. Plus it's lighter and smaller. I'm 6'4" with 37" inseam, and my DRZ has a 2" taller Renazco seat. When I get on the X-bike, the size feels like a pit bike.

Thanks for taking the time to do a write-up.

I've been thinking of some rides I'd like to do with the little bike but don't want to trailer it. In stock form and with some mods it's not much good above 90km/hr (55mph) so long distance highways are kind of out. My questions to you are:
1. How well do you think it pulls up at a real (not indicated) 65mph?
2. Would a longer highway trip be reasonable power wise with this modification?
(obviously a person's butt would be the limiting factor for distance anyway)

Weather has been uncooperative. I'll report back on mileage and speed as soon as possible.

RichardU wrote:

So how does it run? I’ve ridden the bike half a dozen times
and it feels … perfect. It’s literally hard to believe. (And I literally mean
literally, not the current common usage which means not literally.) Every time
I get off the bike, I think, “Is it really that good?” Then I get back on and
realize, “Yes, it’s that damn good.”

The bike has stock gearing, and now it pulls hard in every
one. The fuel injection seems spot on. Only occasionally do I get a mild pop on
deceleration.

Those were pretty much my same thoughts on my first ride; Travis really did a good job with this kit. Did you get the custom modified FMF controller or just the standard one?

Ministry wrote:

Did you get the custom modified FMF controller or just the standard one?

I got the upgraded one.

Would a custom modified FMF EFI controller just have a certain setting? I was always under the impression that the FMF, Attitude, and other various fuel programmers were all manufactured by the same company.

Actually Dobeck is changing the stock settings of the controller to reflect what they did to ours but only on the controller ordered after the change was made last month. the cntrollers curently in stock will more than likely have th eold programming. If you do get one of these Dobeck will reprogramm it for free.

The specific settings spec'ed by FMF, Additude etc will be just as they were. What will be changed is there will be more ajustability for BBK etc. The old programming only allowed for up to a 10% increase the new one will be set for up to a 20%.

ThumperRacing wrote:

Actually Dobeck is changing the stock settings of the controller to reflect what they did to ours but only on the controller ordered after the change was made last month. the cntrollers curently in stock will more than likely have th eold programming. If you do get one of these Dobeck will reprogramm it for free.

The specific settings spec'ed by FMF, Additude etc will be just as they were. What will be changed is there will be more ajustability for BBK etc. The old programming only allowed for up to a 10% increase the new one will be set for up to a 20%.

Thanks for shedding some light on that!

I had a chance to ride the 275 X. Gearing is stock, and all speeds and mileages are indicated. I weigh about 210.

Shifting into 6th felt right at about 65. I could accelerate from there on level to mild grades. At about 82, the acceleration slowed down substantially. Mileage was 56 mpg. I would plan for 50-55.

I hardly ever hit 6th gear on twisty roads. I'm thinking of moving up one tooth to a 43 rear sprocket. Might lose a little bit of top end, but that's not where I ride this bike anyway.

Sounds great! Rode a brand new X at a dealer a week ago. Picking up a used one next week. The test ride was fun, but I can definitely see myself doing some mods for more power throughout the rpm range. I might just do the usual mods before I contemplate the big bore. Has anyone ridden the bike with intake, exhaust, and fi tuner mods for quite a few miles before going big bore? All the dynos I've seen compare to totally stock, and I'm guessing some of the other review people added those mods along with the big bore at the same time. Curious how much just the big bore helps compared to an already modded, well tuned bike.

Keep in mind that you havent really "rode" a WR and became comfortable with it yet. The Power Band on these things is way up top and teaching yourself to rev the piss out of 'em almost constantly takes a bit of time to get comfortable with. In my opinion, the big bore kit is a nice upgrade, and there is no replacement for displacement, but the real question is about reliability and are the power gains worth it? To me, it's like trying to improve the performance of a Hardly Ableson, its just a push rod motor and really, whats the point? If it is that big of a necessity, you may want to seriously consider a larger bore bike to begin with.

I have to agree with SPAGURU, also a stock, fresh off the showroom floor X feels substantially less powerful than an uncorked one. I noticed a big difference adding the FMF programmer, PC4 and pulling off the airbox door.

I would also recommend a pipe, gearing, airbox opening, K&N, and programmer first. Then decide if you need more power. Those mods make a big difference.

Anyway, back to the program. Thanks for the report Richard.
If we say that the indicated is about 10% out, then we're talking about 72mph for reasonable cruising. That's 115km/hr for those not in the U.S.

That's pretty decent. I only like to cruise at 90 - 100km/hr on mine with substantially lowered gearing.

Notice any increase in vibration due to the slight increase in piston size?


On the gearing front Richard, you may want to consider more than a one tooth change as you're not likely to notice that. A lot of folks have gone to a 46t. I have a 48t and really like it. It also gives me the option of swapping for a one tooth larger front when I want higher gearing for a while.

ZED wrote:

Notice any increase in vibration due to the slight increase in piston size?

I have not noticed any extra vibration. Of course, I have also changed to fatbars, which may affect perceived vibration.

Cool

Anymore news/info on the kit??

I've now ridden five days that were 200-250 miles each. This bike is amazingly fast in the twisties. The guys I ride with can out-ride me any day when I'm on my Tiger 1050. On the WRX, I can leave them out of sight in two corners. They tell me I don't even look like I'm trying.

In many ways, I'm not trying. The bike just works. When I lean it over, I realize it's turning much tighter than the road, so I go faster. If something doesn't feel quite right, I can shift my weight imperceptibly, and I'm perfectly balanced again. Some of this is common to all WRX bikes, but I would lose a lot of speed without the big bore.

The big bore adds a lot to the bottom end, I went up one tooth on the rear (because I had a 43 from my wife's WRR) which adds even more. I feel good up to about 75 mph (GPS). After that, it accelerates slowly, but I have cruised at 80 on the freeway with no problem. I'm wondering if I'll ever ride my Tiger again.

For some reason the seat never bothers me. Yamaha got this right by going just a little bit wider than a standard dirt bike, which is all it takes to properly support the pelvic bones. Also, I'm impressed with the engine braking. You really feel it when you drop a gear and let out the clutch.

That's all I can think of for now. I'll be happy to answer questions.

How do you find that front end? Does it come up a lot faster, and how does it feel?

The front wheel of my WR250X spends all of its time on the ground. The front wheel of my DRZ sees some air time over obstacles, and I can easily wheelie my mountain bike, but that's about it.

Any updates on Big Bore kits offered by Thumper Racing and Athena? Performance improvements. Are they worth it?

Greg

Akoffroader wrote:

Any updates on Big Bore kits offered by Thumper Racing and Athena? Performance improvements. Are they worth it?

Actually, yes, now that I see my last response. The front wheel of my WRX now regularly spends some time in the air. Much easier to loft than my DRZ (I'm not very good at wheelies). Just yesterday, I hit the power on a slight rise and I didn't even realize it was up until it lowered back to the pavement. I can also clutch it up with no problem. One side effect, the stock tire lasted 4000 miles. The replacement, also stock, is close to the wear bars after 1500. I routinely run this bike hard. It's insanely fun. Do I wish it was a 450? Of course. But I can't find another bike with the equal ridability and reliability. I put a Renazco seat on it and I can ride all day.

RichardU wrote:

Akoffroader wrote:

Any updates on Big Bore kits offered by Thumper Racing and Athena? Performance improvements. Are they worth it?

Actually, yes, now that I see my last response. The front wheel of my WRX now regularly spends some time in the air. Much easier to loft than my DRZ (I'm not very good at wheelies). Just yesterday, I hit the power on a slight rise and I didn't even realize it was up until it lowered back to the pavement. I can also clutch it up with no problem. One side effect, the stock tire lasted 4000 miles. The replacement, also stock, is close to the wear bars after 1500. I routinely run this bike hard. It's insanely fun. Do I wish it was a 450? Of course. But I can't find another bike with the equal ridability and reliability. I put a Renazco seat on it and I can ride all day.

I want to see pictures of your Renazco....