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Discussion Starter #1
Friends ,
I have a plan to bore up my R25 from 250 cc to 320 cc using R3 Cylinder , pistons and ring piston ...

Yamaha Indonesia not selling that items in Indonesia , anyone can help me ?

Regards
 

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Friends ,
I have a plan to bore up my R25 from 250 cc to 320 cc using R3 Cylinder , pistons and ring piston ...

Yamaha Indonesia not selling that items in Indonesia , anyone can help me ?

Regards
You would also need new heads to match the larger cylinder bore.

Maybe better to trade in your R25 for an R3?
 

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Im guessing you are located in Indonesia and dont have access to the R3?

If you're in a country where they sell the R3 Id say just sell your R25 for an R3. The cost of converting will likely be very high.

Not only is it Pistons/Rings/Cylinders and likely the cylinder head that are different, but I guarantee the ECU has different fuel maps. As well I know the throttle bodies on the R3 are stamped with the R3 model # so there could be a difference in those as well. I found an english copy of the R25 manual once but cant seem to find it again to compare other specs.

If you're really interested in doing it you might want to get in contact with someone in Thailand where the R3 is sold and is closer to Indonesia than the Americas
 

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Discussion Starter #4
You would also need new heads to match the larger cylinder bore.

Maybe better to trade in your R25 for an R3?
Yamaha Indonesia don't sell R3

You mean I must adjust the squish to new bore diameter ? ok ... Noted
but if I don't do that , what is the impact ? higher compression ?

Im guessing you are located in Indonesia and dont have access to the R3?

If you're in a country where they sell the R3 Id say just sell your R25 for an R3. The cost of converting will likely be very high.

Not only is it Pistons/Rings/Cylinders and likely the cylinder head that are different, but I guarantee the ECU has different fuel maps. As well I know the throttle bodies on the R3 are stamped with the R3 model # so there could be a difference in those as well. I found an english copy of the R25 manual once but cant seem to find it again to compare other specs.

If you're really interested in doing it you might want to get in contact with someone in Thailand where the R3 is sold and is closer to Indonesia than the Americas
In Indonesia we have several options for ECU replacement (Stand alone) , like Daytona (300 Usd ) , ARACER (525 Usd) .

yap , any source will do ... if the price still fit in my budget :)

waiting respons from Thai member
 

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Yamaha Indonesia don't sell R3

You mean I must adjust the squish to new bore diameter ? ok ... Noted
but if I don't do that , what is the impact ? higher compression ?



In Indonesia we have several options for ECU replacement (Stand alone) , like Daytona (300 Usd ) , ARACER (525 Usd) .

yap , any source will do ... if the price still fit in my budget :)

waiting respons from Thai member
R25 has a 60mm bore/diameter in each cylinder. R3 has 68mm bore. So the diameter of the cylinder head areas where the valves are has to also have a diameter of 68mm.

The R25 head(s) won't fit on R3 cylinders.

As noted in another post, you would also have to buy a new throttle body assembly, which is larger for the R3 than for the R25.

None of these parts are cheap! That's why it makes more sense to sell, or trade in your R25, and get an R3, IF it's within your budget to do so, and if Yamaha Indonesia will start selling the R3 there. Seems strange that they don't sell it there when the R3s are MADE in Indonesia!!!!!! Is it because there is a limit on engine displacement size? Maximum is 250cc? Or is it just because the R25 is so popular, and such a huge seller, there?
 

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R25 has a 60mm bore/diameter in each cylinder. R3 has 68mm bore. So the diameter of the cylinder head areas where the valves are has to also have a diameter of 68mm.

The R25 head(s) won't fit on R3 cylinders.

As noted in another post, you would also have to buy a new throttle body assembly, which is larger for the R3 than for the R25.

None of these parts are cheap! That's why it makes more sense to sell, or trade in your R25, and get an R3, IF it's within your budget to do so, and if Yamaha Indonesia will start selling the R3 there. Seems strange that they don't sell it there when the R3s are MADE in Indonesia!!!!!! Is it because there is a limit on engine displacement size? Maximum is 250cc? Or is it just because the R25 is so popular, and such a huge seller, there?
No its a displacement tax thing
 

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No its a displacement tax thing
Do you know the reasoning for the high taxation on larger displacement bikes?

It must mean there aren't all that many big bikes on the roads and that mostly only wealthier people can afford to buy them....

That sucks!
 

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Also make sure your clutch is upto par. If not, you may get clutch slip at higher speeds.
If you won't change the gearing, you might actually see a drop in top speed, and mpg.
without the correct counterbalance, your engine might vibrate more, resulting in lower engine life span.
Without proper ecu mapping, you will be running way too lean, with possibly overheating as a result in extreme conditions.
You could somewhat fight off the lean, by fueling BP Premium fuel, which carries about 5% more energy per ounce of fuel than regular fuel.
It's probably the only thing you can do against running lean, unless you plan on running exotic fuels...
 

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Also make sure your clutch is upto par. If not, you may get clutch slip at higher speeds.
If you won't change the gearing, you might actually see a drop in top speed, and mpg.
without the correct counterbalance, your engine might vibrate more, resulting in lower engine life span.
Without proper ecu mapping, you will be running way too lean, with possibly overheating as a result in extreme conditions.
You could somewhat fight off the lean, by fueling BP Premium fuel, which carries about 5% more energy per ounce of fuel than regular fuel.
It's probably the only thing you can do against running lean, unless you plan on running exotic fuels...
Note: What's true for BP gas/petrol isn't consistently true across the wide range of gas/petrol brands available. A lot depends on which type of crude oil the refinery is starting with, Light Crude or Heavy Crude (including which oil field they are sourced from), the refining process(s) used and how the final fuel is blended.

Depending on its blending, a Premium fuel may actually contain less energy per unit volume than a Regular.

Also, since the R3 doesn't have a knock sensor, it may not be able to take advantage of a fuel that has higher energy density to adjust MBT, (Minimum advance for Best Torque) which is the optimal ignition setting for a particular combination of engine speed, load—and fuel. Most knock-sensored engines have their ECUs programmed to actively seek MBT and thus can profit from a higher octane fuel.

The R3, without a knock sensor, can't do that.

RE: Lean running engines. All engines are set to run lean in order to meet air quality standards. Leanness is determined by the ratio of fuel to air in the mixture entering the combustion chamber(s). The energy density of any fuel has no impact on the leanness of the mixture. A higher energy-dense gas will give a stronger push on the top of the piston but will not affect how lean the mixture is.

A richer mixture will run cooler, but if it's too rich then not all the fuel will vaporize, allowing some un-burned gas to exit the exhaust system, creating backfires if that un-burned gas is ignited by the hot muffler or pipe, and the rich mixture can actually wash some of the engine oil off the cylinder walls and other parts, causing extra friction and subsequent heat build-up, leading to abnormal wear.

Premium gasolines do usually have a higher quality additive package than Regular gas does, but this mostly only helps prevent corrosion and build-up of gums and solids in the gas tank. This is a common occurrence in seasonal use or in infrequently run engines.

Gasoline, though it seems like a simple thing, is actually a very complex product. These are the various refinery streams that are blended, in various combinations and quantities, into the gasoline that you put in R3s tank:


Straight-run gasoline, usually also called naphtha is distilled directly from crude oil. Once the leading source of fuel, its low octane rating required lead additives. Between 0 and 20% of this stream is pooled into the finished gasoline.

Reformate, produced in a catalytic reformer has a high octane rating with high aromatic content, and relatively low olefins (alkenes). Most of the benzene, toluene, and xylene (the so-called BTX) are more valuable as chemical feedstocks and are thus removed to some extent.

Catalytic cracked gasoline or catalytic cracked naphtha, produced from a catalytic cracker, with a moderate octane rating, high olefins (alkene) content, and moderate aromatics level.

Hydrocrackate (heavy, mid, and light) produced from a hydrocracker, with medium to low octane rating and moderate aromatic levels.

Alkylate is produced in an alkylation unit, using as feedstocks isobutane and alkenes. Alkylate contains no aromatics and alkenes and has high MON.

Isomerate is obtained by isomerizing low octane straight run gasoline to iso-paraffins (non-chain alkanes, like isooctane).

Butane is usually blended in the gasoline pool.
 
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