New Main Jets?

MyYammiBeetch · Post by **MyYammiBeetch** » Thu Jun 10, 2004 5:55 am

Hi guys I have an 89 exup 1000. I've been thinking of replacing the main jets coz bike is running a bit rich, always starts without choke and does about 100 miles to the tankfull.<img src=http://www.ezboard.com/images/emoticons/ohwell.gif ALT=":\"> I read that they do wear. I have standard air filter and race exhaust should I go for Dynojet DJY 4133 or OE Yamaha ones or not bother and try something else? <img src=http://www.ezboard.com/images/emoticons/sick.gif ALT=":x">

dragracer1951 · Post by **dragracer1951** » Thu Jun 10, 2004 7:18 am

flyingcircus gave this one up a while ago and it's GREAT Before you start playing with the jets, check the float levels and make sure that the vent tubes are not plugged. A way to narrow the list of possible suspects is to do a roll on test. Try second gear, slowly bring the RPM up in gear to 5000 rpm and then nail it. Try the same technique at 7k, 8k, 9k. See if it stumbles when you nail it. Test all these rpm again, but this time bring it up slowly to the target RPM, then quickly let off to idle and nail it. If your bike does not stumble with test 1, but does with test 2 then you have an rich pilot circuit condition. If it stumbles with both tests, at any of the rpms listed, You have a rich main jet. If it stumbles in the mid rpm, and not at the higher rpm for test1, then the needle jet is rich. Try that out and see how it reacts. Jim by the way....what dj jets are in the bike? the jets don't wear but the emulsion tubes do and what jets are in the kit you are thinking of?

MyYammiBeetch · Post by **MyYammiBeetch** » Thu Jun 10, 2004 8:15 am

Cheers Dragracer sounds like a brilliant solution I've never noticed a stumble as such but I will try these anyway. Trouble is I'll have to fix me rev counter first! It's about the only thing that's not working on the bike at the moment, but that the way it goes innit. I havn't really looked at the carbs yet but I suspect they are standard apart from being derestricted (British Spec) The dynojet ones I quoted are the reccomended stage 1,2 & 3 jets. I was under the impression that 'emulsion tube' was american for jet if anyone can clear that one up it would be appreciated. Cheers, I will let you know how I get on.

dragracer1951 · Post by **dragracer1951** » Thu Jun 10, 2004 10:15 am

I was under the impression that 'emulsion tube' was american for jet if anyone can clear that one up it would be appreciated. Cheers, I will let you know how I get on. Yeah....it's also called the needle jet. that's what the main is screwed into Jim and you don't really need a tach...just try ar successively higher revs low , some mid and high

MyYammiBeetch · Post by **MyYammiBeetch** » Fri Jun 11, 2004 3:16 am

Cheers Jim. I had a play on the bike this morning, no stumbles as such anywhere, she gurgles a bit like a (dare I say it) 2 stroke at a steady 2 to 3 thousand rpm holding the throttle steady and the exhaust pops when going downhill with the throttle backed off and I'm sure it doesn't leak anywhere coz I stripped it and replaced all the gaskets last week. It might be the race can. So the next step is new plugs and balance the carbs the old plugs may reveal something. I will have a look at the main jets while I'm at it and let you know what they are. Thanks again Russ.

Cosmo007 · Post by **Cosmo007** » Sun Jun 13, 2004 1:27 am

These are the tubes that the needle is centered within. The area of fuel atomization. Changing needle height has its effect within the emulsion tube first.

MyYammiBeetch · Post by **MyYammiBeetch** » Mon Jun 14, 2004 4:40 am

Swapped the plugs, the old ones where a healthy colour so I reckon the jets must be OK, but I got a guy to re-shim the valves about 5k miles ago and he fitted the plugs and they where too wider gap. I ground back the negative electrode a bit on the new plugs as recommended by Chuck D (cheers Chuck) balanced the carbs and now she's running sweet as a nut. I did notice some oil around the bottom of the threaded part of the old plugs, is this bad? I didn't investigate which main jets are fitted as the old plugs where such a healthy colour (sorry Jim). She still starts without choke and pops at the exhaust though.

flyingcircus68 · Post by **flyingcircus68** » Mon Jun 14, 2004 7:01 pm

The oil on the threads could be a sign that your starting to burn oil. How often do you top off? Does it smoke when you first start it, or when you drop the hammer? It might be the valve seals. If you don't have an oil coat on the base of your plugs, its probably no big deal yet. If your popping when you let off, its either a bad sync. or the idle mixture is uneven or lean. You might have to clean out the idle circuit.

dragracer1951 · Post by **dragracer1951** » Tue Jun 15, 2004 3:50 pm

Have ya noticed that the solution to a lot of these problems is that the carbs are dirty???? I think I'm startin to see a trend here!!! <img src=http://www.ezboard.com/images/emoticons/eek.gif ALT=":eek"> <img src=http://www.ezboard.com/images/emoticons/eek.gif ALT=":eek"> <img src=http://www.ezboard.com/images/emoticons/eek.gif ALT=":eek"> <img src=http://www.ezboard.com/images/emoticons/eek.gif ALT=":eek">

flyingcircus68 · Post by **flyingcircus68** » Tue Jun 15, 2004 7:45 pm

I just wanted to add the following to be clear: valve lash has a direct affect on the vacuum level at idle, so that should be rechecked if you are going to re-synch. Otherwise, the sync job will cause markedly different butterly positions between all the carbs and cause wacky differences in idle mixture.

dragracer1951 · Post by **dragracer1951** » Wed Jun 16, 2004 6:34 am

Hear him!! Good point Jim

MyYammiBeetch · Post by **MyYammiBeetch** » Fri Jun 18, 2004 3:32 am

Hi guys , thanks for all the input. The bike uses about a litre every 2000 miles, Cruising down the motorway 80 to 100 mph seems to use more oil than scratching down country roads etc. She's always (last 5 years) used about the same amount so I can live with it for now, until something more serious develops (please no!). Is it possible to swap the camchain without removing the engine from the frame? (89 FZR 1000 exup)

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New Main Jets?

New Main Jets?

jetting

Jets

jets

Jets/ Richness

emulsion tubes

Jets

Re: Jets

clean

Re: clean

Valves

Oil Burning