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We work on porting to achive the best results for you and your applicaton. This is not a one size fits all service. We will make your cylinder head flow propperly at the propper lift points . We use mathmatical calculations based on your engine come up with the required air flow. Most service centers over port and you actually lose air flow.




We offer a wide variety of maintenance solutions for the owners of modern 4-stroke dirt bikes. Our service offerings range from total engine rebuilding to individual component servicing and performance machining. Our aftermarket and OEM parts and accessories give you the choice of the best brands like Wiseco, Cometic, Advanced Sleeve, Hot Cams, KPM Black Diamond, Revolution, Xceldyne, Hot Rods, Cylinder Works, and Vertex.

We know how to fix your late model 150, 250, and 450 dirt bike engines. Most of the attention nowadays is on used 250Fs so the next paragraphs are dedicated to those models. However the riding and mechanical situations are the same for 150, 250, and 450 dirt bikes. The service packages listed below cover a wide model year and range.


We fix 250Fs to be reliable and inexpensive to operate. If you want a reliable engine that has a low hourly operating cost and a wide range of optional aftermarket parts and accessories, send you engine to us. We specialize in building 250Fs to be strong performers and reliable. It’s common for customers to call us and say that they’ve got 100hrs on their bikes without even a valve adjustment. We don’t build $10,000 45hp time bombs that cost $750 per engine hour to operate. Try the “race teams” if you want over-priced high maintenance engines.

We offer many services for 250Fs from simple top end rebuilds to 300cc big bore strokers. We’ve developed an extensive database of every aftermarket engine component and can help you put together the best performance engine rebuild to suit your needs. We offer free teardowns and estimates on engine rebuilds, and our cylinder head service is the most important thing you can do to increase the reliability of your 250F.

Now if you’re one of those cheapskate knuckleheads who just want to glue your basket-case 250F engine together so you can Ebay-it to some unassuming dumbass and pass your problems onto someone else and involve us in a product liability lawsuit, please call our competitors instead. And if you’re one of those guys who has a buddy that went to a 1-year crash course in motorcycle mechanics at a local high school and he’ll fix your engine for a 6-pack of Miller High Life but he just needs to call us and ask us how to do a step-by-step rebuild of your engine over the phone. In that case, please call our competition, they’re friendly guys who love to answer tech questions for free. Make sure you use the toll-free number so you can save money and be mo-cheaper. Maybe they can sell you a sticker, t-shirt, or some colored bolts to fix your engine for a reallyreallycheap price.


All 250Fs blow-up at some point, they were designed to do that from the Japanese manufacturers in order to make you buy new bikes and lots of parts. They also blow-up because of some typical riding and repair situations;

You downshifted twice instead of just once over that big tabletop jump and when you landed the engine mechanically over-revved and the valves collided into the piston and destroyed the engine.You ran your bike way longer than you should have and never serviced the top end and the valves are sacked out and you have to push-start your bike or pull-start it with a ATV just to get it running and its really slow and pops a lot and shoots fire out the exhaust. Now it has no compression and won’t start no matter how fast that ATV pulls it.You reasoned that because crude oil has been trapped in the Earth’s crust for 65 million years that you could skip a couple of oil changes or 10 and now your engine has been running for a while with no oil. Now every bearing needs to be replaced along with a lot of really expensive parts.You crashed your bike and it laid on the right side running wide open. Meanwhile the oil sump in the engine is located on the left side and starved for oil and just sucked air, which makes a pretty crappy lubricant. The first thing to seize was the camshaft journals, which use bare aluminum as a bearing surface, and yeah that’s a really stupid design and obviously you don’t own a Honda!Your buddy who knows everything (no not really) helped you rebuild your top end for a 6-pack and didn’t know exactly how to set the cam timing but figured it would jump into place the first time you bounced it off the rev limiter but it blew your engine up instead and now he doesn’t hang around your garage anymore telling you about how he knows everything, because he doesn’t really know anything except how to cost you money.Instead of up-shifting when the power peaks you bounce it off the rev limiter. But every time you hit the rev limiter you increase your engine hours by 10 minutes for every second the engine sputters, rendering your hour-meter useless. Eventually the valves and springs get fatigued and fail causing the valve heads to break-off, you can guess the rest!

We can fix all of these problems, no problem, as long as you have money. If you don’t have money, that’s a problem! In that case you should part-out your blown-up underwater 250F on Ebay and get pennies on the dollar for it. If you want to fix it right, here’s what we offer in the way of package deals on parts and services.


The average stock 250F costs $50 per engine hour to operate for beginner and intermediate riders who never hit the rev limiter. Expert amateurs? Figure $90hr. This is only a contribution to engine parts and performance machining using OEM replacement parts, not gas and oil. Pro Supercross Lites racers can expect to budget $750hr. The reason the price increases so dramatically is that the engine has to be built to the edge to be competitive and the racer’s demands are greater. After we rebuild the engine with high quality American-made accessory parts (averaging $1,500 parts and labor) you can expect to lower the cost per hour to about $15hr. The average hours per season of practice and racing in a 7-month season is 50 hours.

Here is a list of recommended service intervals for intermediate amateur riders quoted in engine running hours.

Oil and filter change 1 hour

Valve adjustment 5hrs (KPM or Xceldyne stainless steel valves 25hrs)

Piston change 10hrs (Wiseco piston 50hrs)

Cylinder head service with valve train replacement 50hrs (KPM/Xcel 150-200hrs)

Bottom-end engine rebuild with crank and bearing replacement 75hrs (Hot-Rod heavy-duty crank and bearing kit 200hrs)

CYLINDER HEAD SERVICE $225 (Labor only, valve train parts your choice)

It’s all in your head! The cylinder head has the most fragile moving parts and is the number 1 source of catastrophic engine failures on a 250F. If you fix it before it destroys your engine, you’ll save a lot of money. We can fix damn near anything for less money than the manufacturers charge for new heads. Ever since the earthquake in Japan and the Libyan war crisis, the price of OE parts coming from Japan and for KTM have skyrocketed. We sidetrack the high prices and mediocre quality of the OE parts and their global-calamity pricing, instead we rely on higher quality, price-stable American-made parts like KPM Black Diamond stainless, Xceldyne titanium, and Revolution Machine valve train parts. Stainless steel or titanium, we can recommend the best parts for your riding demands. The cylinder head service package includes disassembly, cleaning, porting, valve guide replacement, multi-angle valve job, assembly, and valve adjustment. Send the complete cylinder head with cams, caps, bolts, and valve cover. We also offer free diamond honing for the cylinder and discounts on piston and gasket kits from $199 and Hot Cams from $155 each. Your bike’s head will be ready to installation!

BIG BORE KITS $450 Parts and Labor

Most 250F cylinders can be bored 2-3mm or 262 and 270cc about 2hp and 450s pick-up about 22cc or 4hp. These kits include over-boring, plating, honing to the cylinder and a piston kit with over-sized gaskets. Big bores improve the throttle response and torque across the rev range. We are an installation center for CYLINDER WORKS 270cc big bore kits and can modify the crankcases for these thicker cylinders. We can match HOT-CAMS and heavier springs for big bore tuning.

ENGINE REBUILDING $350 (plus parts) 15-20% OFF PARTS

Usually when we get an engine, it’s completely destroyed because of one of the 5 reasons listed above. The average price of a 250F engine rebuild is $1,900 and that includes rebuilding the head, replating the cylinder, replacing the crankshaft and main bearings, and all the seals as well as the tedious task of completely disassembling and cleaning all the components of a 4-stroker engine. We offer free telephone estimates based on your honest description of the damage and pictures. We do not accept partially disassembled engines or basket cases. There is no warranty available on any 4-stroke engine repairs or the original and aftermarket parts and accessories we sell.



CRF150R 2007-12 162cc

CRF250R/X 2005-12 262cc


KX250F 2004-09 262, 270cc


RMZ250 2004-09 262, 270cc


YZ250F 2001-11 262, 270cc

YZ400F 1998-99 420cc

YZ426F 2000-02 444cc

YZ450F 2005-09 472cc


Print a copy of the Service Order Form and follow the directions on packaging your parts for shipping. All the options are listed for services, powerband choices, fuel types, spare parts, shipping methods, and payment options.

Finish Line Engines LLC

431 madison St

Beaver Dam Wi 53916

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