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Post by mark2009 on Apr 8, 2009 20:03:58 GMT
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Post by teejayexc on Apr 8, 2009 21:45:29 GMT
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Post by mark2009 on Apr 9, 2009 8:57:32 GMT
Heya many thanks for your reply. I had a look at my bike and there are no metal washers over the carb intake ports like the above photo. I will have a look if there are any plastic type ones in the air intakes tonight.
I have booked the bike in with yamaha to see if they can work out what the problem is, because I belive my bike should go quicker than 80mph! They said on the phone that is sounds like its been restricted to 33bhp if its only doing 80mph and doesn't stutter or smell like its running rich etc.
Can anyone inform me of any other types of restriction to look out for so i can have a gd look this weekend? photos would be great!
thank you.
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Post by Flymo on Apr 9, 2009 9:46:04 GMT
there is also another kind of washer that goes in the rubber between the carbs and the inlet monifold, see this thread Flymo |
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Post by General Gman on Apr 9, 2009 10:08:32 GMT
Mark,
The black blocks you can see in the carbs are the carburretor slides... and the carbs won't work without them.They certainly are not restrictive in any way.It may be, however, that you have restrictors in the carb tops to prevent the slides from rising fully - this was a method used on ZXR750 models to restrict them to 100BHP back in the day.Could you take off the carb tops and post a picture ? -and wehereabouts are you ? if you're anywhere near Slough I'd be happy to come and take a look.
Dave
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Post by mark2009 on Apr 9, 2009 10:29:26 GMT
hello guys, many thanks for all your replys. Im going to whip out the carbs tonight to have a good look. I didn't see any option of being able to post photos on the forum but obviously some people can! Dave many thanks for informing me what the blocks are. I started the bike briefly to see how far they would retract, i say on full throttle the still cover 40 - 50% of the intake. Does that sound like a restriction? I am in rutland, not near slough im afraid.  I will hopfully workout how to upload photos onto the forum tonight. |
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Post by mark2009 on Apr 10, 2009 17:11:56 GMT
well i got down to the carbs but couldn't see any form of restriction as suggested above. The bike is gona have to go into the garage to get sorted.
In Peterborough Taz motorcycles is offering free dyno runs this month, so I will get the old XJ on to see what its putting out.
watch this space!
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Post by General Gman on Apr 12, 2009 7:53:43 GMT
If the slides arent lifting fully, then I think you have an air leak / vacuum problem somewhere (or all your diaphragms are shagged).I can't remember offhand .At wide open throttle, the slide should go all the way up and you should just se the needle.Can you lift the slide all the way by hand ? if not, then there must be something in there stopping them opening all the way.
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Post by mark2009 on Apr 13, 2009 17:42:11 GMT
ahhhh is this true? --- when i move the slide by hand it doesn't go all the way into the chamber. however when i turn on the bike I would say about 40 -50% of the throttle slides will stay in the chamber on full throttle.
I took off the inlet manifold today and had a look but there was nothing there to restrict the flow at all.
Also today i made the following observations on ridding:
5th gear at 6500 RPM I will be doing an indicated 80mph.
4th gear I can (just) get it to rev to 7500RPM and an indicated 85mph.
(no stuttering or coughing, bike pulls cleanly)
does this sound right to you?
Also is there any chance the bike could be restricted in the exhaust or in electrically in an ECU?
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Post by pilgrim on Apr 13, 2009 18:47:45 GMT
There's a cable problem or deliberate stop on the cable (restiction of some sort). Exhaust side restriction is very unlikely as not letting out what has already happened can be, well, terminal.  (True 2T engines are reliant for back pressure in the exhaust to resist too much fuel transfer before next ignition as it's on the same stroke, btw) Electrically, maybe, but the bike isn't really hi-tech, beam me up scotty stuff. Easiest control is what can be burnt in the cylinders, ie: fuel flow before ignition. Just thoughts..... |
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Post by mark2009 on Apr 14, 2009 18:58:26 GMT
when u say restricted cable - do u mean a restriction on the throttle cable? Or do u mean a restriction stopping the throttle piston retracting all the way in the carb body itself?
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Post by CD on Apr 15, 2009 9:00:44 GMT
When the grip is twisted the carb throttle valves should open fully. On CV carbs, the slides open according engine demands so only open 100% when the engine is running more or less flat out.
Remove the airbox and push each slide - it should actually lift all the way. When you do that you can see the throttle valve which should alo open 100% with the twist grip.
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Post by mark2009 on Apr 15, 2009 12:10:58 GMT
When the grip is twisted the carb throttle valves should open fully. On CV carbs, the slides open according engine demands so only open 100% when the engine is running more or less flat out. Remove the airbox and push each slide - it should actually lift all the way. When you do that you can see the throttle valve which should alo open 100% with the twist grip. I have had the airbox off and looked at the slides. they defiantly don't retract all the way when pushed with the engine off. I thought this may have been normal and the engine wasn't running. What could be restricting them retracting fully? I have the haynes manual, if anyone could tell me the part I should be looking for inside the carb, as a possibly restricting the slides, i will have a look. thankyou! |
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Post by General Gman on Apr 15, 2009 12:50:38 GMT
OK, take the tops off the carbs - is there a plastic spacer between the carb top and the slide, possibly inside the spring ? if there is, just remove it and the slides will lift fully and you'll be able to enjoy full (!) power  |
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Post by mark2009 on Apr 15, 2009 18:33:04 GMT
i really am looking forward to getting home from uni now and having a look. i will be so proud if i can de-restrict my bike!
I will let you know how I get on!
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Post by mark2009 on Apr 21, 2009 17:36:24 GMT
I just got the bike back from yamaha, they charged the earth but its no longer restricted! horayyyyyyyyyyyyy! The restriction was u guessed it in the top of the carbs, stopping the throttle slides retracting fully. I tried to get the bolts off myself last weekend but they were sezied on. otherwise I would of done it myself. Just had the bike at 115 mph (indicated) Much better, im alot happier! |
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Post by volomoto on Apr 24, 2009 12:36:06 GMT
This thread sounds like the same as I'm experiencing with my '98 XJ600N. I did the valve shims and balanced the carbs, but still only get 80-90mph out of it.
How can I tell, and exactly what part is being referred to when you say "take the tops off the carbs"?
Any suggestions or help would be appreciated.
Grant.
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Post by General Gman on Apr 24, 2009 20:18:31 GMT
The black plastic (on most) caps at the opposite end of the carb to the float bowl.
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Post by volomoto on Apr 25, 2009 13:30:15 GMT
I think that sounds like what I would call the "vacuum chamber cover". I've taken one off, and found a big lump of plastic in there (see attached photo) which appears to be what was preventing the diaphragm and piston from retracting fully. I've checked the Haynes manual and that lump of plastic isn't on the carb diagram so I've taken it out and re-assembled the carb (will do the same for the other three too). Then I'll re-balance the carbs and give it a test run. I will report back if I don't kill myself test riding my newly de-restricted XJ600N.  |
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Post by CD on Apr 25, 2009 13:32:48 GMT
Removing these should not affect the carb balance. If its running smoothly probably best to leave the settings as they are.
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Post by volomoto on Apr 25, 2009 16:59:47 GMT
WOW!!! ;D I've got a new motorbike and it didn't cost a penny ;D The four bits of plastic are now in their final resting place - the bin. 110MPH NO PROBLEM - Not saying where  Can't wait for the Welsh National Rally now. Of course I won't be able to keep up with my mates Fireblade but at least it won't be embarrassing now. Thanks to everyone that contributed to this thread, without it I wouldn't have known my Naked Divvy had been hobbled. Grant. |
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Post by teejayexc on Apr 25, 2009 17:01:32 GMT
WOW!!! ;D I've got a new motorbike and it didn't cost a penny ;D The four bits of plastic are now in their final resting place - the bin. 110MPH NO PROBLEM - Not saying where Can't wait for the Welsh National Rally now. Of course I won't be able to keep up with my mates Fireblade but at least it won't be embarrassing now. Thanks to everyone that contributed to this thread, without it I wouldn't have known my Naked Divvy had been hobbled. Grant. Don't throw 'em in the bin , someone else may require 'em!! Glad you got your bike back though  |
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Post by volomoto on Apr 25, 2009 17:36:27 GMT
Actually they're not in the bin now, my mate with the Fireblade told me to keep them so that "when he buys it off me next year" he can re-restrict it for his missus to ride (meanie). My XJ isn't even for sale, the cheek.  Now it's full power it's going to take much longer to grow out of.  |
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DHARQE
Scooter Rider
Posts: 50 
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Post by DHARQE on Aug 14, 2014 0:36:02 GMT
i got the same issue, 95mph max, mine has no restrictors in at all, nothing between the carbs, throttles open fully, diaphragms are fine, nothing in the tops to restrict. had this issue ever since i got the thing, it runs great, just 95mph max!.......stumped
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Post by amorti on Aug 14, 2014 11:18:18 GMT
You need to check - do the butterflies open fully? are there plastic things as above in the carb tops? are there restrictor plates in the engine, which you usually find bolted under the intake tracts or sometimes as washers in the carb to engine rubbers? At 95mph top whack it definitely sounds like a 33hp restricted bike.
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