Tyre width?

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Tyre width?

Post  big boar, little man on Sun Nov 22, 2009 6:15 pm

About three months ago I changed my sprockets and chain. The 14 48 was geared too high in the tight stuff so I went to a 14 52. Was very happy with the results. Alot more selection of gears. The tyre was well forward, which I have heard helps with tight turns? I was finding after a ride, evidence of tyre rub on the exaust and even on the right side of the rear mud guard. This was with a half worn kenda 120. The tyre sat straight in the swing arm, and there was no slop in the bearings. I have recently changed the tyre to a 110 which I've only been on a few small rides with so far, thus the verdict is still out on this narrow tyre, Anyone else found this problem?
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Re: Tyre width?

Post  Kiwi650 on Mon Nov 23, 2009 11:18 am

Have meaty 140 on mine and have the tyre rub marks you speak of on right hand side, mate got a 4.6 wide on his and has the same mark. Was told on here 120 is the standard/factory width. 110 might be getting bit narrow ? 100/110 are fitted to XR250's, KLX300's here in NZ.
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Re: Tyre width?

Post  big boar, little man on Mon Nov 23, 2009 9:10 pm

I've got a 140 on my xr 500, I find the thing wants to come out from under me especially on grassy tracks when I come out of a rut or something, But this new 110 I've got on my 650 I havn't given it a real chance yet. One things for sure, it dosn't look cool. See how it goes and if its no good, hopefully by the time its chewed out the chain might have stretched enough so a 120 sits far enough back to not rub.
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Re: Tyre width?

Post  Kiwi650 on Tue Nov 24, 2009 1:55 am

Yeah go to wide and you lose having centered ground pressure, think I'll be going for the standard 120 wide.

That's probably why my back wheel is set right back on the adjusters - big 140 rear.

(As posted elsewhere on here - Would not be surprised at all if Honda has set the whole handling of the bike around their recommended tyre sizes being 120 for the rear)
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+1

Post  Bump on Tue Nov 24, 2009 8:19 am

And I think there's a note on here from Ogilvie about running the rear wheel as far forward as possible.
Kiwi650 wrote:Yeah go to wide and you lose having centered ground pressure, think I'll be going for the standard 120 wide.

That's probably why my back wheel is set right back on the adjusters - big 140 rear.

(As posted elsewhere on here - Would not be surprised at all if Honda has set the whole handling of the bike around their recommended tyre sizes being 120 for the rear)
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Re: Tyre width?

Post  Kiwi650 on Tue Nov 24, 2009 11:21 pm

I tried searching for posts by the legend but could not find any readily at this stage, has he posted on here or is it references by him I should be searching ?

Usually less overall tension on your whole drive chain with shorter chain - less work to do, Interested in his reasoning ?
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Bruce Ogilvie’s list of tips ...

Post  Bump on Wed Nov 25, 2009 5:52 am

There are a few versions of this list posted online. Some I know have been doctored and are wrong. This one seems all correct.


Bruce Ogilvie’s list of tips on things American Honda has discovered or learned over the last year of testing and racing the big XR.

THINGS RACERS NEED TO KNOW
·
Read and follow carefully the February/March Wrench newsletter for conversion to full power competition mode and for right footpeg installation. They recommend checking the right footpeg bolts for tightness on a regular basis, about 300-mile intervals.
·
Final drive gearing of 14/45 for BITD and 15/48 or 15/47 (Mexico) for SCORE events offering a smoother power delivery and the best (forwards) wheel placement. (Stock is 14/48)

Remove the brass reserve from the petcock and run in the on position.

Do not use a rear mousse or tire insert. Use only a heavy-duty tube.

If you use the stock fuel tank, you must remove the white plastic insert so our (Honda pit) dump cans are able to completely fill your tank.

MORE TIPS FOR EVERYONE

The air filter is held securely in place by the left sidepanel. Be sure the front lower clip has adequate tension. It can be bent or damaged by a riders boot or other impacts, which decrease tension on the air filter and can result in dirt by­passing the air filter at the front lower corner.

With only a 1.7 quart oil capacity, usage becomes more critical (1 pint low is more than a 25 percent reduction in total capacity). Be sure to check oil levels in 200-to-300 mile intervals. To get a proper dipstick reading, the engine must be left at idle for 20 to 30 seconds. When racing, idle into the pit on which you plan to check the oil. Also watch out for overfilling; too much oil can destroy the crankcase seals.

A stock XR650 will run better on pump gas than a high-octane race fuel, which needs a higher com­pression ratio to be effective. (All gas in the Honda pits is Chevron 92- or VP 93-octane unleaded.)

Keep the rear wheel adjusted as far forward as tire clearance allows. The bike turns and handles better and is more stable with the wheel adjusted closer to the swingarm pivot.

The stock chain uses a staked/clipless master link (endless chain). A bike with this much torque will break conventional clip-type master links. Using one is asking for a race failure.

Honda sells the D.I.D 520 ERV2 chain (0-ring with staked master link). The Honda part number is DIDS2OERV2-120. Team Honda has been using this grade of chain since 1994. A special tool is required for staking the master link (also available at your Honda dealer). The stock XR650 chain is also very high quality and meets or exceeds the ERV2 strength measurements.

The rear fender bolts tend to come loose and should be checked regularly or have a thread-lock applied. {Precision Concepts used RV Silicone-PM}

Inspect on a regular basis the spring-loaded part attached to the choke plate on the carburetor rear intake opening. If the spring breaks from fatigue (from excess running with the choke on or half on), it can lead to the flapper being drawn into the combustion chamber and cause engine failure. An alternate solution is to remove the flapper and spring from the choke plate, which can be done while still in the carburetor. The only drawback is the bike might take three kicks to start when cold.

For optimum suspension performance overall machine balance is critical. Example: forks will have a harsh deflective character when the rear rides too low into the stroke. Pay careful attention to setup and rider sag. We have found that between 95 and 100 mm seems to be the best to keep proper front to rear balance.

Do not use oversize discs or our spare wheels will not interchange. Our pit spare front wheels are all XR600R front wheels that will fit onto a 650 when used with our (pit provided) wheel spacers.

The owner’s manual is incorrect: reserve is actually 0.53 gallon.

Install a second rear rim-lock in the rear wheel. Safety-wire spokes in both wheels after break-in (tighten spokes and balance wheels also).

If you have experienced a boil-over situation with your coolant, consider switching to a radiator cap with a 1.6 or 1.8 rating (stock is 1.1). Honda doesn’t make a 1.8, but a KX8O cap is rated at 1.8 and will fit. The downside to going to a higher rating is it puts more pressure in the system, especially the hoses and fittings. This increases their susceptibility to punctures and other damage. Remember, this liquid-cooled bike should not sit and idle for long periods without airflow through the radiators. Additionally, the system is designed to boil over and has a coolant catch to handle the escaping fluid. This does not equal overheating, a common misconception.

The Baja race bikes use a 1.8 cap without the overflow tank and thermostat to save weight. They are able to get away with this by careful bike warm-up and racing with the bike wide open. These mods are not for the average rider!

The power-up kit is the same as used by Johnny Campbell and company and adds about 10 horsepower with a higher-compression piston, different cam and a stronger cam chain.

Honda also leaves the chain guide alone because it believes the polypropylene part will flex with a hit, while a metal guard will bend and do more damage.
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Re: Tyre width?

Post  Kiwi650 on Wed Nov 25, 2009 7:09 am

Cheers Bump for posting that, any chance of spliting it into a seperate topic ? Think could be big topic if has not been done before

A stock XR650 will run better on pump gas than a high-octane race fuel, which needs a higher com­pression ratio to be effective. (All gas in the Honda pits is Chevron 92- or VP 93-octane unleaded.)
I've been using BP 98 ultimate as it says in the Honda supplied manual to run an octane of 98 or higher, stated burns cleaner and leaves less damaging deposits. Hard move for me going against what Honda recommends, am I better off putting 95 unleaded in ?

A similar article I read recommended a 95 KX500 radiator cap which I think makes more sense, a KX80 may have a high pressure cap.
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NOT SURE...

Post  Bump on Thu Nov 26, 2009 11:36 am

There may be a difference in octane ratings between there and here. I'm in So Cal and run Chevron 91 in everything I own. My dually will go 30K mikes on a fuel filter if I run Chevron and only 7K miles or less if I run other brands. I'm not sure why but I got sick of saving a few cents on gas and then having to change fuel filters.

I suggest running the lowest octane you can. When I was on a race boat team years ago that was our experience. The higher the octane the more difficult it is for the gas to ignite. I don't know if that means slower burning as well.

Running race gas might be the same problem as running some racing oils in that they lack certain additives to run long distances.

Not sure about the cap. If you run Evans NPG then the cap and the rest don't matter. I run the stock cap, Evans NPG-R, Fluidynes, and the SS Xrsonly thermostat unmodified.


Last edited by Bump on Thu Nov 26, 2009 9:15 pm; edited 1 time in total
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Re: Tyre width?

Post  Kiwi650 on Thu Nov 26, 2009 12:19 pm

Its British Petroleum BP Bump and its their 98 BP ultimate unleaded pump gas, we get your american Mobil here, the octane level is a misnomer in some respects its the RON count that matters.
Higher the octane level the easier it is to ignite like racing gas, and why they will not even let you fill your bike while seated on it (tried doing so to keep the beast level to get as much gas in as possible) in case you fall of it lolol and cause a spark and send "The whole shooting box up in flames"
Higher the octane unbelievably makes your motor run cooler - another possible reason why Honda lists in the factory supplied manual 98 octane or higher
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must be dfferent over there.

Post  Bump on Thu Nov 26, 2009 9:11 pm

Over here octane is a measure of the resistance to detonation. Higher equals higher. So we need higher RON here to prevent dieseling in high compression engines. Or a LOT of combustion chamber engineering and computer control of timing, fuel delivery, and so forth. As I recall there are a few ways to measure that resistance.

When we travel to American states with high elevations, say Colorado for example, I'm always surprised at the lower octanes available in gasoline. I reckon with less O2 available they want a little more volatility in their gas to balance out their fire triangle inside the cylinder.

Diesel over here is odd to me. It's made to ignite under pressure without the aid of a spark. If you pour it on to something it is difficult to ignite. Our Forestry people down in So Cal have to mix it 1:2 with gasoline to start control fires.

http://en.wikipedia.org/wiki/Octane_rating

It looks like England has octane ratings similar to yours: http://www.petrolprices.com/about-fuel.html

We haven't generally seen octane numbers that high over here since the 1970s at regular gas stations. But upwards of 100 is only for serious race stuff or older cars with high compression and low tech combustion chambers. It all changed here when Reagan deregulated drilling in the USA. It was highly regulated until then so a driller who went deeper could charge more for his oil. And the Koch Brother's pipeline had to buy it at that price. He took away the incentive to drill deep here in the USA. After that is was all about finding and delivering oil as cheaply as possible. Hence our plunge into Saudi Arabia where it's just below the surface. I could be wrong but I think lower octanes are cheaper to refine, deliver and sell.

Team Honda uses Chevron 91 in all their race bikes for offroad and MX and Supercross.
Kiwi650 wrote:Its British Petroleum BP Bump and its their 98 BP ultimate unleaded pump gas, we get your american Mobil here, the octane level is a misnomer in some respects its the RON count that matters.
Higher the octane level the easier it is to ignite like racing gas, and why they will not even let you fill your bike while seated on it (tried doing so to keep the beast level to get as much gas in as possible) in case you fall of it lolol and cause a spark and send "The whole shooting box up in flames"
Higher the octane unbelievably makes your motor run cooler - another possible reason why Honda lists in the factory supplied manual 98 octane or higher
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Re: Tyre width?

Post  Kiwi650 on Fri Nov 27, 2009 10:26 pm

We haven't generally seen octane numbers that high over here since the 1970s at regular gas stations.
What - New Zealand got something the USA does not - wonders will never cease .

Yep the British figures similar to here Bump.

Team Honda uses Chevron 91 in all their race bikes for offroad and MX and Supercross.
I'll just stick with the 98 plus recommendation by Honda, suspect team Honda bikes would be poles apart from mine, different compression, timing etc, More octane More Horses.
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Re: Tyre width?

Post  Thumper GUY on Fri May 07, 2010 5:28 am

Hey BUMP now that pump fuel has methanol in it, is there a benefit to running Methanol free? Is it easier on gaskets in the carb or is that too a Myth?
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Free is best

Post  Bump on Fri May 07, 2010 10:29 pm

I can't recall the whole story but I read several places that methanol free is best for dirt bikes.

Thumper GUY wrote:Hey BUMP now that pump fuel has methanol in it, is there a benefit to running Methanol free? Is it easier on gaskets in the carb or is that too a Myth?
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Re: Tyre width?

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