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Re: So you want to rebuild a 1st Gen 1100 shock (Pt.1)

I created a downloadable pdf of DPike's above rebuild how-to. It includes a fleshed out reassembly process and current rebuild parts numbers and prices from raceTech's website.
 

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Re: Understanding Carbs

Found this online. May be helpful in troubleshooting your carb problems

Your engine is basically an air pump, and your carb meters how much air and fuel are sucked into that pump. Even though they may differ wildly in size, shape and design, all four-stroke carburetors have the same basic parts or circuits. Your slide cutaway (or throttle valve) needle and needle jet will all affect your bike's acceleration from one-quarter to three-quarters throttle, and this is the most important area for off-road riders, since we spend the most time at these throttle settings. Due to the hassle of making changes to these circuits, these are the most neglected areas of tuning. Too rich jetting (too much cutaway, needle positions too high, too large a needle jet) can make your bike lunge and hard to control. If it's too lean in this area, the bike will feel really flat and down on power, but will respond quickly to changes in throttle position. It may detonate (ping) under a load too. Pinging can also be caused by too little octane or winterized fuel (oxygenated, blended with additives), so keep in mind any fuel changes if your bike suddenly starts detonating in otherwise "normal" conditions.

Your main jet is probably the most talked-about circuit, and it's as critical to get it right on a four-stroke as with a two-stroke. The main kicks in at half throttle and takes over metering duties as you hit full throttle. If your main is too rich, the bike will sputter and surge as it tries to burn all of that fuel. Too lean, and the bike will run flat or have a flat spot in the powerband. A severely lean main will cause your bike to seize just like a two-stroke. It's better to be slightly rich on the main than slightly lean, because it will run cooler.

Yamaha's new 400s have an accelerator-pump circuit. This system squirts a stream of raw fuel into the carb venturi every time you wick the throttle. Think of it as the four-stroke's PowerJet carb - it richens the mixture to run best at lower engine speeds, yet allows a leaner top for more over-revs. If you radically modify your engine (flowed head, hot cam, etc.), you may have to richen this circuit slightly, but it's otherwise not something you mess with for mere weather or altitude changes.

Your pilot jet (or slow jet) controls the idle circuit, or from zero to one-quarter throttle opening. The pilot jet and airscrew control the amount of fuel and air going into the engine at slow engine speeds. It's very important to tune these circuits because they control throttle response and starting. The pilot circuit has a major affect on how well your four-stroke starts -or refuses to start - after a fall. At every event we attend, there is always some four-stroke rider who comes into the pits with his bike revving wildly. Invariably, this rider will say that his bike is hard to restart after a stall, so he turns up the idle adjuster so it won't die.

That's like jumping from the frying pan in to the fire. Thumpers are only hard to start when they are jetted poorly or when the wrong technique is used. The rider who turns up his idle is only perpetuating the myth about thumpers being hard to start. Most manuals (and this magazine) tell you that you should not touch the throttle when you kick a thumper. Well, turning the idle up is mechanically opening the throttle, right? You will make, your bike even harder to start. You have to fix the problem, not the symptoms of the problem!

Carburetor Jetting Tricks
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General Carburetor Jetting Tricks
Your bike’s owner's manual is a great source for recommended jetting and tuning tips. If you bought your thumper used and don't gave a manual, get one. Set the idle speed as per your manual. If it won't start easily using the manual's technique, your pilot jet is the likely culprit.

Whether your bike is air or water cooled, you should start it and get it up to race temperature before tuning the pilot circuit. A hotter engine will run leaner than an old one, so failure to properly warm the bike will result in a too-rich setting. With the bike up to temp, adjust the airscrew so that the bike runs and responds best to slight throttle movements. Now, kill the motor and see how many turns out you have on the airscrew. Less than one, and your pilot is too lean. More than two, and it's too rich. Install the next-size pilot and repeat the test.

Most off-road bikes are jetted lean to meet emissions standards, so you will likely want to richen these circuits, especially if you have gone to an after-market pipe, air filter or even removed OEM baffles (pipe and/or airbox). If you remove the muffler diffuser, you should toss the airbox stuffer too, or the airbox won't be able to draw enough air to feed the engine. Most aftermarket companies will give you recommended jetting, so use this as a baseline.

Under most conditions, about the only time you will need to go leaner on an EPA-legal four-stroke is because of altitude. Air is thinner at higher altitudes, so it contains less oxygen, and your jetting will be too rich. You will want to go down a size on the pilot, one or two on the main and lower the needle a position (raise the clip).

Cold air is denser than warm air, so it holds more oxygen. On cold mornings, your jetting will be slightly rich, but thumpers are less susceptible to changes than two-strokes. Where you might change the pilot on a two-stroke when it's really cold, an airscrew adjustment will suffice on a thumper.

The same is true for barometric pressure. As the barometer rises, the pressure compresses the air, and your jetting will be slightly lean. A falling barometer causes a rich condition, but thumpers don't care about the weather as much as two-strokes.

Four-Stroke Carburetion Troubleshooting
Overall, the Yamaha YZ400F is jetted almost perfectly from the factory; however, it is very picky about its air filter. Do not over-oil the filter, and do not expect it to start immediately after oiling the filter. Let it sit overnight (not in the cold) to allow the carriers to evaporate. Better yet, keep spare filters in a plastic bag so that you never put a freshly oiled filter in the bike on race day. Modifications throw stock jetting out the window, so this troubleshooting guide will apply to the 400F as much as any other four-stroke.


Bike Won't Start After a Crash
Pilot too lean
Idle set too high
Improper starting procedure


Bike Runs-On or Won't Idle Down When Throttle is Chopped
Idle set too high
Air leak in intake or engine
Pilot too rich (when bike is hot)


Bike Wont Start When Cold Temp Outside
Pilot jet too lean
Air filter over-oiled
Motor oil too thick for temperature
Carburetor Jetting Tricks
Technical Article Sponsor


Bike Sputters / Wont Clean Out at High RPM
Main jet too rich
Air filter over-oiled
Spark plug has debris on electrode


Bike Coughs & Stalls in Slow Turns
Pilot jet too lean
Idle set too low
Valves set too tight
Decompressor is set too tight, so turning the bars engages release slightly


Bike Hesitates or Bogs Over Deep Whoops or G-Outs
Float level too low
Carb vent tubes blocked
Main jet splash shield not installed
Float level too high, gas is trapped in vent tunes (install T-vents)


Bike Starts But Wont Take Throttle Without Sputtering
Pilot jet too rich
Water in fuel
Debris in main jet


Bike Suddenly Starts Sputtering / Gas Flows from Vent Tubes
Stuck float check valve
Debris in gas or carb


Bike Runs Hot / Feels Slow & Flat on Straights
Main jet too lean
Fuel octane too low, causing detonation


Bike Coughs & Stalls When Throttle is Whacked Open
Needle too lean
Slide cutaway too lean
Pumper circuit blocked or too lean
Source
 

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Re: Understanding Carbs

Been having the usual problems with my BST38's on the GSXR7/11, wearing out the tubes. I was looking at doing the spacer trick but as I think has been mentioned in the thread, along with the needles tilting the other main cause of the problem is the slide guides wearing, causing the slides to move and the tubes to wear.

My carbs have done about 67000 miles and on the last carb strip down I actually checked the guides and found that they were very worn, there was also a visible build up of material that had come from the guides.

Although replacement guides are not available from Suzuki or Mikuni, it seems that other manufacturers who use the BST carbs have obviously noted the problem and do sell the guides as a spare part.

The closest match I have come across is some guides for a BST40 carb listed by KTM (code 58431037000), the overall dimension of the guide is identical, the only difference is the main hole through the middle of the slide which I presume is 40mm instead of 38, i have fitted a set and apart form having to drop the needles by 1 groove, the bike is running perfectly.

Only time will tell if this has solved the problem, but at least I can be sure for the moment that the guides wont be causing it.

The only down side is that in the UK the guides cost about £23.00 each, hopefully they should pay for themselves in better economy and not having to change the tubes every year or so.

Hope the above helps.

Matt.
 

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How-To: Front Fork Overhaul/Spring Swap




1. Outer Tube
2. Inner Tube
3. Inner Anti-Friction Sleeve
4. Outer Anti-Friction Sleeve
5. Oil Seal Retainer
6. Oil Seal
7. Oil Seal Stopper Ring (Clip)
8. Dust Seal
9. Compression Damping Force Adjuster
10. Damper Rod
11. Lock Nut
12. Top Cap
13. Damper Retainer Bolt + Copper Washer
14. Spring
15. Spring Seat
16. Spacer
17. Spring Seat
18. Spring Retainer
19. Fork Cap
20. Fork Cap O-Ring
21. Preload Spring Adjuster
22. Expander (Metal O-Ring)
23. O-Ring
24. Ball Bearing
25. Rebound Damping Force Adjuster
26. O-Ring

NOTE: (9)Compression Damping Force Adjuster and (10)Damper Rod Are NON-Servicable

Things you will need:

Tools:
-Spanner Wrench
-15mm wrench
-14mm wrench
-8mm hex wrench
-long socket and extension
-fork oil (10 Weight for Canada as per service manual)
-Flat head screwdriver
-Bucket (a blue one)

All Balls Fork seal kit:
-Oil seals
-Fork wipers

Cleaning
-Brake Cleaner Spray
-Diesel
-Rags/Shop Towels

1. Raise the bike off the ground and remove front wheel, rotors, wheel fender, and bracket holding forks together. Loosen the clip-ons.

2. Using the spanner wrench, loosen the fork cap about 1/4 turn. This is to break it loose while it's still held by the front fork clamp.


3. Place some rags under the forks and loosen the 8mm hex bolt on the bottom of the forks. I did this by using the hex key and sliding a long socket and extension over it for leverage. Just break it loose. Some people have had a hard time with this, and either use a special tool or an impact driver. I had no problems with mine and it snapped loose with a bit of pressure. The compressed spring was enough for the damper to not spin.


4. Slide the forks out of the bike.

5. Begin unscrewing the fork cap. When the o-ring is visible, place a rag over the cap and slowly continue unscrewing it, holding it away from your pretty-boy face. When the cap comes off, you will feel a slight push up.

6. The inner tube will want to slide down. Let it slide down. Quickly flip the fork over into the bucket and let the oil drain out. You can pump the inner tube a few time to get some oil out.

7. Now we want to tackle the spring and top cap. I was able to wiggle a 14mm wrench in between the spring retainer and top cap. I put a 15mm wrench on the spring adjuster and loosened them. At this point, the top cap can be unscrewed off the damper and put aside. Flip the fork again and drain more oil out.


8. Loosen the lock nut to relieve preload on the fork. Do NOT remove it completely. The spring will pop off! Once I felt I could handle compressing the spring down enough by hand, I pulled down on the spring and shook the fork a bit to get the spring retainer to fall off, then I carefully released the spring and the whole spring assembly came off the damper. Flip the fork again and jack off the damper. It will ejaculate what's left of the oil.




9. Pull on the damper and from below, loosen the 8mm hex bolt until the damper comes loose, then pull it out.

10. To remove the inner tube, you need to remove the dust seal, the seal stopper ring (clip) and the oil seal. To remove the dust seal, place a dull screwdriver between it and the outer tube. Tap the screwdriver so it seats below the dust seal and begin twisting the screwdriver to work the dust seal loose. Then pull it off.

11. Remove the seal stopper ring by prying it away from the outer tube using a screwdriver. Be careful not to scratch the inner tube chrome. Pull it off


12. To remove the oil seal, hold the inner and outer tubes and begin sliding them apart. Small but swift and firm taps will begin to unseat the oil seal. Keep sliding them until they come apart. slide off the oil seal and oil seal retainer (Big washer)


13. There are two anti-friction sleeves that are seated on inner fork tube. Carefully slide the small one off and by prying on the larger one, slide it off the bottom.

14. Moving to the top cap, it is comprised of three parts; The fork cap, the rebound adjuster and the preload adjuster. To dismantle them, screw the preload adjuster in all the way. It will come out of the bottom. To remove the rebound adjuster, screw it down all the way into the preload adjuster. When it comes out, a small ball bearing will also pop out. Do NOT lose it.


15. Remove the compression damping force adjuster at the bottom of the outer tube using a 14mm wrench.
 

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Re: How-To: Front Fork Overhaul/Spring Swap

Cleaning

CLEAN EVERYTHING!!










For the fork tubes, I dipped a foam-tipped bottle brush in diesel and brushed inside both tubes. I followed up with brake cleaner to get any residue out. As for the fork dampers, I put the bottom in a can of diesel and pumped the damper about 3-4 times. On the third pump, it will shoot diesel out the top. Make sure you pump slowly, and try not getting it in your eyes!

 

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Re: How-To: Front Fork Overhaul/Spring Swap

Reassembly

1. Wipe down the inner fork tube. Install the inner anti-friction sleeve on the bottom.

2. Cover the bottom of the tube with some saran wrap and slide on the dust seal, oil seal stopper ring (Clip) Oil seal, oil seal retainer, and outer anti-friction sleeve. (Note: For oil seal, writing on seal faces up)


3. Make sure outer tube is clean of lint and debris. Place the inner tube into the outer tube. Seat the outer anti-friction sleeve into its slot in the outer tube, then press it into place. It should seat all the way in. The drop the oil seal retainer over it (that big washer)






4. Slide the oil seal down and press it into place. I found the best way for me to do that was to slide the old seal over it and use a screwdriver to push them both down, then pry out the old one.







5. Install the oil seal stopper ring (Clip) and "click" it into place


 

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Re: How-To: Front Fork Overhaul/Spring Swap

6. Slightly oil and slide the oil seal down and press it into the outer tube. To seat it, I found the easiest way for me was to cut the old oil seal, put it over the new seal, then use a screwdriver and a hammer to tap onto both of them to get them into place. I then pried out the old seal.







7. Slide down the seal retainer clip and "click it into place




8. Slightly oil and slide down the dust seal and press it into place. I tapped mine down with a socket and a rubber mallet. I worked my way around it.




9. Put the damper rod into the fork tubes and install the 8mm hex bolt. When you feel the damper rod start to spin, just pull on it slightly and it should do the trick. Torque to spec.




10. Install the compression damping force adjuster with a 14mm wrench and torque to spec.
 

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Re: How-To: Front Fork Overhaul/Spring Swap

Installing Springs/Spacers

1. Begin by putting the top cap back together. If you removed the 0-rings and expander ring, apply a dab of fork oil to them before sliding them back onto their components. Install the o-ring onto the rebound damping force adjuster and screw the adjuster into the preload spring adjuster.

2. Slide the o-ring of the preload spring adjuster into place, and slide the expander on halfway. Insert the ball bearing into the hole on the side of the preload spring adjuster and slide the expander over it.

3. Apply fork oil to the preload spring adjuster o-ring and screw it into the fork cap.



4. Set the preload fork adjuster to halfway, or the forth line from the top. Set the rebound damping force adjuster to 1.5mm above the preload spring adjuster




5. Loosen the top cap lock nut all the way down. Slide on the spring and two spring seats (washers). Screw the top cap onto the damper rod until the damper rebound force adjuster slightly seats onto the damper. Once seated bring the lock nut up to the top cap.


6. Place the spring retainer onto the top spring seat. Push the lower spring seat against the spring, then measure the distance between the two (measurement a)


7. Slide the inner fork tube all the way up towards the top cap and measure the distance (measurement b)


8. In a vertical position, we want the top cap to be resting (on the spring, seats and retainer) 20mm higher than the fully extended inner tube. In this instance our measurement b was 25mm, but we only need 20mm. This means the measurement a must be 25-20=5mm shorter. That will be the length of the spacer


9. Cut the spacers




 

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Re: How-To: Front Fork Overhaul/Spring Swap

10. Install the spacer. In my case, there was a bit of play in the damper. It would move up-down 5mm before contacting the spring retainer. This is OK. When we compress the assembly, this slack will be eliminated.



11. Extend the inner tube up all the way and measure the distance between the bottom lip of the fork tube and the top of the inner tube. It should be 20mm. In my case, it was almost 21mm. I can live with that


13. Remove the top cap, spring seats, retainer clip, spacer and spring. Tie a piece of wire to the damper rod. Add oil (407ml US, 452ml Canada) and begin pulling up on the wire. The damper will begin filling with oil. Oil will start to come out of the top, so pull up slowly, then either press it back down and repeat or let it slide down by itself. Do this about 10 times. Then hold the wire up and slide the inner tube up/down about 10 times. Place the assembly to the side for about 10 minutes.




14. Slide on the spring, spring seat, spacer, spring seat and retainer clip.




15. Just as before, screw on the top cap until it lightly sits on the damper rod.


16. Tighten the lock nut and preload spring adjuster using 14mm and 15mm wrenches.

17. Slide the inner tube up and recheck that the gap is still 20mm. Apply fork oil to the top o-ring and simultaneously compress and turn clockwise to close the fork assembly. Tighten shut


18. Slide the fork into the fork clamp and line up the mark with the top part of the clamp (10mm)



CONGRATS FUCKTARD!!

Now go do it all over again
 

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Re: How-To: Front Fork Overhaul/Spring Swap

Excellent write-up. Only thing I would add is to use a large Crescent wrench or proper sized open end/box wrench on the fork caps so you don't chew them when you remove/install them :thumbup
 

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Re: Understanding Carbs

Hey,yeah another guy with carb problems,can some one point me in the right direction,new to this forum site,cheers
 

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I am having a front brake problem. I have a 1988 gsx1100f, front brakes worked fine when I parked it. had too change fluids out for it has been sitting for a couple of years. I accidently let the master cylinder go dry, now I cant get it too bleed. tried gravity feed an nothing. dealer is telling my my master cylinder is bad, but I just rode it an parked it an it worked fine. any help on how too get air out of the system would help a lot. an which caliper do I start with an which bleed to I open first. it has two caliper's on the the front with 4 bleeder screws
 

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I am having a front brake problem. I have a 1988 gsx1100f, front brakes worked fine when I parked it. had too change fluids out for it has been sitting for a couple of years. I accidently let the master cylinder go dry, now I cant get it too bleed. tried gravity feed an nothing. dealer is telling my my master cylinder is bad, but I just rode it an parked it an it worked fine. any help on how too get air out of the system would help a lot. an which caliper do I start with an which bleed to I open first. it has two caliper's on the the front with 4 bleeder screws
Rebuild or replace the master cylinder. It's your front brakes... You don't want to piss around with your stopping power. A new master cylinder isn't that pricey; it'll cost maybe $30 A new master is less than $100.

I replaced both mine (brake/clutch) with new Hayabusa masters. They look just like OEM but take adjustable levers.
 

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Re: So you want to rebuild a 1st Gen 1100 shock (Pt.1)

I created a downloadable pdf of DPike's above rebuild how-to. It includes a fleshed out reassembly process and current rebuild parts numbers and prices from raceTech's website.
Yeah, it's a long time after the fact but thanks for this.

Other than the 20mm difference, does anyone know if these P/Ns are the same for the 1st 750 limited shock (which also has the external reservoir)?
 

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Re: So you want to rebuild a 1st Gen 1100 shock (Pt.1)

Yeah, it's a long time after the fact but thanks for this.

Other than the 20mm difference, does anyone know if these P/Ns are the same for the 1st 750 limited shock (which also has the external reservoir)?

I would certainly think so.
My biggest question would be if those springs that are available on that site for the 1986 GSX-R 1100 would fit on the LTD shock lengtwise.

If the LTD shocks are also 25mm shorter, maybe these shocks got a spacer on the damper mechanism as described in the how-to.

If I have my LTD spring removed, I can ask the guys from Racetech about the length of my spring.
 

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clutch deglazing

Borrowed from another site.

Clutch disks; remove the contaminants with brake cleaner then lay
each plate over a 400-600 grit black dry emory paper and rotate in a
circle... you're just removing the glaze, don't get carried away and
remove too much material. You should end up with a friction plate
looks dull like a new one as opposed to a shiny glazed one.

Plates; Check the pressure plates for "bluing" caused by localized heat...
make sure they are not warped. Remove the contaminants with brake cleaner
and brass wire wheel them to erase the blue and also to generally scuff
up the surface... you should end up with a dull surface clean & free of spots.
marks...
 

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Unbelievable thread, glad I found it.
One question regarding the 1100 shock being put on a 750, from what I've read here it is fairly simple, cheap, and gives at least a minor improvement in handling (not to mention they're rebuildable). Is this correct? Basically buy one and slap it in? I'm interested in throwing one on my 88 750.

Thanks guys
 
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