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Old 07-08-2010, 03:03 PM   #1051
switch
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Quote:
Originally Posted by Bluesmudge
Do you know what the length of your longer brake line is?
115cm (~45-46 inches) should suffice when it comes to replacing the original brake line.

Could you post a picture of your cable routing? Thanks!




Regarding front sprockets: for dommies, 14T-16T is the norm. 13T is too small -- there's not enough metal for chain integrity -- not to mention the fact that the chain will probably chew into the swingarm quite fast.

Try a bigger rear sprocket -- 15-45 is stock. 14-49 should do nice.
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Old 07-08-2010, 03:24 PM   #1052
Big_John
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Quote:
Originally Posted by Bluesmudge
Do you know what the length of your longer brake line is?

I don't remember, but I measured the stock line and had the company build the new one 2" longer. It is perfect.
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Old 07-08-2010, 04:26 PM   #1053
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Quote:
Originally Posted by Fatguts McCantRide
Is there any option for fitting a manual decompressor somehow?
Yeah, install the head cover from an '88-00 XR600 and the cable/lever to match. I doubt you'll be able to kickstart it without one if you have no automatic decompressor.

Quote:
Originally Posted by switch
Compression is controlled by the valves. Which are controlled by the camshaft. You can't have stock compression with a non-stock camshaft.
Now you're talking about dynamic compression which is reliant on the valve timing events. Static compression ratio does not change regardless of what the valves are doing. Static compression is just a measured/calculated best-case scenario; dynamic compression is rarely as high as static.

Quote:
Originally Posted by switch
I've seen two failing so far due to engine mods. One was also posted on these boards, too. The other was a friend of mine who put a 10:1 compression without an oil cooler and rode the thing like he stole it. Shot a 2 sq inch piece of the cylinder skirt sideways and totally wrecked everything above the crankshaft (including the crankshaft itself, which isn't really serviceable).
I doubt your friend's broken connecting rod was the direct result of not having an oil cooler. Even the worse cases of lubrication failure that I have seen have not resulted in a broken, or even damaged big end on the conrod. Rarely the bearing cage will fail and result in a broken rod, but that is quite rare.
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Old 07-08-2010, 05:34 PM   #1054
Fatguts McCantRide
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Awesome, thanks for that info HT! What’s the difference between the XR600 and the XR650L carbs, apart from a 1mm smaller butterfly? (42 v 41mm). The 600 is $200 cheaper than the 650L, I can handle a drop in performance for half the price. Will it fit into my 92 Dommie or am I wasting my time?
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Old 07-08-2010, 08:21 PM   #1055
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The 650L/NX650 carb is CV(constant velocity) type while the 600's is a more familiar round slide. The 600 carb won't cost any power and the throttle response will be better. I'm not sure about cables, but I'm relatively sure that the 600 carb will fit in the rubber boots just fine. The 650R carb is another option. It is very similar to the 600's, but is slightly larger. As a result, it is a pretty tight fit in the engine-side boot.

I would consider a pumper carb before any of those if I was looking for a replacement, however.
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Old 07-08-2010, 10:06 PM   #1056
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Knowing absolutely zilch about carbs, until you just posted I assumed flat slide and pumper were marketing terms rather than real descriptions. Guess I've got some researching to do tonight!
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Old 07-08-2010, 10:23 PM   #1057
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The Mikuni HSR series is a less expensive pumper to find new, but variants of the Keihin FCR are easier to find used because they come stock on so many MX bikes.
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Old 07-09-2010, 03:26 AM   #1058
Brad Felmey
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Quote:
Originally Posted by Fatguts McCantRide
Knowing absolutely zilch about carbs, until you just posted I assumed flat slide and pumper were marketing terms rather than real descriptions. Guess I've got some researching to do tonight!
"Pumper" means it has an accelerator pump. The stock carburetor does not have one. This is a mechanism that delivers an extra shot of fuel when the throttle gets whacked open quickly. This improves response and eliminates a delay or dead spot.
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Old 07-10-2010, 04:35 AM   #1059
jj5
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Just bought a Honda NX 650

1988 with rear diskbreak
32K KM (+/- 20K miles)

Some kind of upgraded rear shock which is adjustable in height. Steal break line for front brake. Steer risers. Rest is pretty much original.

Tires (dunlops trailmax rear and front metzler tourance) en chain and sprockets are good as new so hopefully i can ride worry free trough the summer.

I start off with a question right away. It also has a oil temperature meter and after a 30min 25KM ride over some highway (never got above 110KM/h or 70MPH) and little bit of city riding it raised to 120C (it was fine on the highway only got up to 120 once i entered the city and had to wait alot at traffic lights). Is this normal? Have to say its a damn hot day with temp of around 30C (86-90F).


And after it got to 120C (248 F) it sounded like something iron was shaking in the engine or somewhere else on the bike not sure about that yet. Only occurred when you revved it. Is this something that sounds familiar?


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Old 07-10-2010, 06:40 AM   #1060
Fatguts McCantRide
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Quote:
Originally Posted by HeadTrauma
The Mikuni HSR series is a less expensive pumper to find new, but variants of the Keihin FCR are easier to find used because they come stock on so many MX bikes.
I see. Man, I'm getting confused the further I go! Are all the linkages fairly common or do I have to find an NX specific one? Eg would this work;

http://cgi.ebay.com.au/KEIHIN-FCR-MX...item1c13e641cf

And Brad, regarding what you mentioned, is the fuel pump a part of the carb or a seperate setup ala EFI stuff?
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Old 07-10-2010, 08:26 AM   #1061
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Quote:
Originally Posted by Fatguts McCantRide
I see. Man, I'm getting confused the further I go! Are all the linkages fairly common or do I have to find an NX specific one? Eg would this work;

http://cgi.ebay.com.au/KEIHIN-FCR-MX...item1c13e641cf

And Brad, regarding what you mentioned, is the fuel pump a part of the carb or a seperate setup ala EFI stuff?
Think either carb will need at least an airbox adapter. Noss Machine makes them for the FCRs, but I don't know what the HSR requires. The auction you linked is for an FCR-MX, which I believe tends to fit tighter under the tank on XR600s and 650Ls. I don't know what it looks like under the seat of an NX650, sorry.

The accelerator pump is a diaphragm pump integrated into the carburetor and is fed by the main fuel inlet. Ever had a Holley, Carter, or Autolite carb apart? If so, it functions in the exact same way as the accelerator pumps on those.

Quote:
Originally Posted by jj5
1.) I start off with a question right away. It also has a oil temperature meter and after a 30min 25KM ride over some highway (never got above 110KM/h or 70MPH) and little bit of city riding it raised to 120C (it was fine on the highway only got up to 120 once i entered the city and had to wait alot at traffic lights). Is this normal? Have to say its a damn hot day with temp of around 30C (86-90F).


2.) And after it got to 120C (248 F) it sounded like something iron was shaking in the engine or somewhere else on the bike not sure about that yet. Only occurred when you revved it. Is this something that sounds familiar?
1.) 120C/250F is nothing unusual for oil temperature. Start getting concerned when it approaches 150C/300F.

2.) If it's actually coming from the engine and isn't something else rattling on the bike, then it wouldn't be a bad idea to have a look at the valve clearances and valvetrain. If you're new to these dry sump RFVCs, be sure it has oil in it and don't check it cold; ride around until it comes up to temperature, shut it off, and check immediately. Just set the dipstick on the threads to get a reading.
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1995 XR628R -Lots of goodies...room for more.
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Feels like I'm livin' on a chain gang."

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Old 07-11-2010, 02:44 AM   #1062
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Hmmz ill drive it around again today cos when i fired it up this morning there was no sound. Also not when i revved it.

I know from cars that you hear the valves best when the engine is cold so guess that should be the same for bikes since its basically the same mechanism in a different package. Are there any other sounds that you start hearing when the engine is warmed up but you don't hear when its cold?

I will refresh the oil and oil filter anyway since the last owner could not tell me when it was last done since he only had it for 4 months and drove 1K on it and didn't do any maintenance in that time.
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Old 07-12-2010, 02:55 PM   #1063
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Often the valvetrain in these engines will actually get louder as the temp comes up. I suspect it does this as the oil thins out.

Some contrasting trivia is that the Honda GX160/200 utility engines' lash will open up as the engine gets hot, not get tighter. Lots of kart racers set the lash extremely tight on a cold engine for this reason.
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Old 07-15-2010, 12:44 AM   #1064
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and a loud valve train means? Something serious broken or some adjusting of the valves?
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Old 07-15-2010, 01:24 AM   #1065
switch
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Quote:
Originally Posted by jj5
and a loud valve train means? Something serious broken or some adjusting of the valves?
You need earplugs. But a valve adjust should do it.
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