HELP! Is having a rev limiter necessary? Digital speedometer install.

Hi fellow old bike fetishists!

So I'm building an XJ 900 1983 scrambler/brat style bike. Currently I am in the process of replacing the original speedo-cluster with a cheap, chineese, digital speedometer/tachometer. When mapping out all the cables I found the cable going from the original cluster going from the "rev/limiter switch" (as Haynes manual describes it). Looking around on the forum I found out that the rev limiter on XJ 900 bikes are switched in by the original tachometer. I'm bummed out and feel like such a noob for not realizing this earlier and I'm now at a crossroad.

Question 1: Is it entirely necessary to have a rev limiter on this bike as I don't see it likely that I'll ever reach those high RPM's on the bike? (I mean, I might mess up a shift and flick my wrist and destroy the engine... But maybe that unlikely enough to not worry about it )

Question 2: Has anybody encountered this dilemma before and found a good replacement/aftermarket rev limiter or figured out how to incorporate the old cluster's rev limiter into the new state of the bike?




Any help or comment immensely appreciated!!!

 

Don't worry about it, a shift light is better though!

 

Not that big of a deal then I guess?
Don’t feel like I need a shift light tho, exhaust is plenty loud to tell me it’s time to shift

 

most of the "multi-function" Chinese speedos have a rev limit indicator light ,you can set at the revs you want.
looks like following the drawing, the rev limiter switch grounds out the t.c.i., dunno if it acts on both coils or just one, but i think i would prefer the indicator light.
just sayin.
stu

 

rev limiter is so you do not exceed redline. there are after market tci to eliminate the rev limiter I do not think it is available for your bike. I have seen them for the vstar because they did not come with a tach.

 

Thanks for the input guys!!!!
I’m gonna risk it without rev limiter. Too complicated for me to install a vstar tci into this bike... But would love it if somebody found a simple rev limiter installation alternative.

 

Guess you can easily do without the rev limiter.

Bought an expensive (and very awesome) German speedo & rev. counter 15 years ago. Works perfectly.
The rev. counter can bee configured so when you meet a specific rev ex. 8.500 revs. per minute - you will have some LEDs to light up. Its not an electronic "motor break" , not connected to the TCI - just a visual signal, but its absolutely bright and clear. Works like a charm.

I guess yours have the same feature.

And as others says - you will be able to hear it when your revs come near 8-9000 revs. per minute.

Good luck.

 

None of the other XJ models of that era had rev limiters.
As for shifting by the exhaust sound goes....you'll be surprised to find that there is not a discernable difference in the sound between 7k and redline. And there is no change at all above redline. Hook up a shift light. Your engine will thank you.

 

As mentioned above, XJs don’t have limiter. I have analog tach and digital speedo on my bike with Max parameter memory and if I remember correctly I over revved my engine to 12xxx rpm (wasn’t intentional) without issues so far.

 

The XJ900 does. The TCI cuts spark when redline is exceeded.

 

Yes the Yellow wire with the black stripe if my memory serves me correctly.

 

Thanks guys! Really helpful!
Found out something else about the bike tho....
I have most likely been riding it for a season without knowing it was only running on 3 cylinders.... I even synchronized it lol.....
Opening another thread about it

 

Hi!

Sylinder number one on my XJ 900 1983 31A wont run (header doesn't get hot like the other ones) and I have probably ridden my bike for about a season with only 3 cylinders firing (guy who sold it to me didn't inform me so he probably did too for a few years....). I bet it's a new record of dumb dumbness..
AAAAnyways, the spark plug in number one is carbon fouled, the other sparks are fine. I tried switching plugs, didn't help. I tried switching sparkplugs leads, nothing. I did a compression test, cylinder 1-3 are all on 134 psi and cylinder 4 is at 150 psi. I did a carb clean a few months ago, but I dould have missed something. Rejetted it (bought "stage 2" jets on ebay sinse bike has pereiod-correct aftermarket exhaust, and it wouldn't run without choke before, it does now, on 3 cylinders..)

1. Can a choke malfunction, mixture screw adjustment, other carb stuff cause a cylinder to not make header pipe hot like the others?
2. Since I "synchronized" the carbs with only 3 cylinders running, could I have adjusted them so bad that one cylinder isn't getting any fuel at all? or just way to much?
3. Are there small passageways where air travels in carburator that might be blocked?
4. Could something in the carb not allow fuel to pass? (I even sprayed starter fluid directly into carb number one while engine was running and good plug was in cylinder, nothing...)
5. Could one of the cylinder header pipes be blocked, mice?

Any help would be extraordinarily apreciated!!!!!!!

 

Check spark in #1, could be bad cap, wire or coil. You can also swap wires of cylinder 1 and 4 since they both fire at the same time. If all is well, time to progress to step 2.

 

already tried, cylinder still dead

 

Did you forget the rag you stuffed in the intake when you had the carbs off?

 

Is there any damage at

A ruptured diaphram on the slide on the dead cylinder would have the same effect, choking the airflow as the slide would not rise. Surely the compression figures would rule the rag left and ruptured diaphram as causes.

 

What you haven't mentioned are your valve clearences. Check they are all in specification before working on your carburettors.

 

Did you clean the carbs, or did you refurbish the carbs?
Just a cleaning won't do.
The rack should have been broken, and every part removed from the carb bodies for cleaning, inspection, and replacement of the old rubber parts. Then the float heights set, and the carbs synchronized.

My bet is that you missed something.

IN THE CHURCH OF CLEAN

 

Merging threads.
One per bike. More than one makes it easy to miss things.
I can rename the thread for you if you'd like.

 

If you have inspected the spark plug and have it correctly gapped and found nothing wrong, other than the obvious lack of spark, but the same plug it will spark when placed in another cylinder. Check the plug caps for corrosion or missing parts. Some plug caps have a resistor built in others don't. Iam not sure about xj900s. Check the spark plug wire, remove the cap and see if there is visible corrosion or burned wires, the wires will look greenish or white and powdery like flour if corrosion. If either is present, and if you have enough length in your wire, trim 1/4in off of the wire. This should be on the same end that the spark plug cap was removed from. Corrosion can cause an intermittent miss fire or a complete lack of fire/dead plug. If you can trim the spark plug wire for a clean connection because your wire is to short or for whatever reason, buy new ones for all or the cylinders and start fresh. If that does not fix the issue check the coils themselves.

 

If you are STILL NOT GETTING SPARK.
Don't get frustrated yet. Now you should your tci box. Your tci box actually controls the "what", "when", and "how much" of the spark. So that means which plugs fire, how often those plugs fire, and how much fire, or electricity is sent to the plug to create the spark. The tci box can be very expensive or damn near impossible to find for most XJs. Let's first check and see if you have the correct TCI box for your bike. All TCI boxes are NOT the same. The box for an xj650 can run an xj750 and vice versa, but you will lose performance and that usually can be seen most noticeably by terrible gas mileage. The correct tci box is the only one you should use. OK so now that you've got the short and sweet version of how the tci works, and possibly checked the current price for a very expensive "maybe-it-works' box on ebay, double check your ignition coils. Is one of the wires that runs out of the black plastic cylinder shaped housing possibly pinched maybe against the frame and a bolt or nut, or could it have been caught between the frame and gas tank, could have possibly the wire insulation vibrated right off of the almost 40yr old bike, was the a hungry rat or rodent? Check make sure. OK your bike should have a tci box with a black foil decal with TID14-19, 31A-10 wording. It is used on all 1983-84 XJ900RK and RL models. (Thank you Chacal and all your awesome parts catalogs).

 

TCIs can cause firing problems, they can cause you lose one or more cylinders. The fine-wires that run from the terminal plugs to the internal circuit board inside the TCI box may become broken,disconnected, or lose a soldered point or "joint" fixing this can help restore an intermittent or an absent spark. A soldered joint fails and must be re-soldered. A bad soldered joint, that may appear ok but isn't, is normally a cold joint they look dull in-color. You can resolder those points. The wires to the circuit board are fine and very thin, and could break from ruff handling to vibrations. Then there burn or blown transitors that may need replacing. If you have never worked on anything like this, now might not be the time to try. There are people that can and are very successful at this type of electronic repair. Go to Chacal's xjparts catalog, TCI Units, under the Electrical System follow the instructions.

 

https://www.xjbikes.com/forums/threads/xj-parts-catalog-section-d-electrical-system.44641/

 

Good luck, I hope it is an easy and cheap fix.

 

Sorry, that would be awesome thanks

 

So youre saying the fact that compression is good means diaphram is likely good and no rag is left in there?

I can see the slide move up and down when the bike is running and I twist the throttle, I haven't compaired it to the other slides tho.. And I am almost certain I did not leave a rag in the cylinder. BUT if I did, could it be blocking the exhaust header?

 

I don't feel like reading that book... watched a few youtube videos about Mikuni cleaning tho. I cleaned jets and replaces main jet and pilot jet using brake cleaner. I inspected the floats and set them according to haynes manual.
I inspecte the diaphram, all looked good and slides moved easily. I haven't taken seperated the carbs from eachother and cleaned the parts in between. HOWEVER, i did the trick where you connect a hose to the float bowl, release the fuel and see how far it climbs, it did not climb higher that the float bowl gasket.

 

Is checking the valve clearences hard ? do i need to buy a new headgasket for that? I'm trying to keep it cheap and would rather leave things be if I don't absolutely have to open the engine up...

 

A rag in the inlet port could never block the exhaust header. A rag in an inlet port would have to get past the inlet valve into the cylinder and out of the exhaust port to block the header. If a rag was left in the exhaust port that could get into the header but your compression figures are the same in 1, 2 and three. Valve clearences is the first check l would do. They are critical to getting the carbs set up properly.

 

No head gasket needed. The valve gear is under the camshaft cover. It's not expensive to check valve clearances for an owner. But you need to use the zip tie method or the Yamaha tool. It's expensive for a shop to do it and that's why some owners don't get them checked, and one of the reasons engines do not run as Yamaha designed them to run.

 

https://xjbikes.com/forums/threads/airhead-valve-adjustment-with-pics.14827/

Read this guide first. Valve adjustment is not opening up the engine just the top cover.

 

Yes.

 

https://xjbikes.com/forums/threads/tech-topic-the-real-costs-of-maintenance.14581/

 

Repairing your bike cheaply can be more costly in the long run.

 

So you didn't really clean the carbs, and for all you know they have never been properly cleaned and refurbished.
You might be OK, but you will be back inside of the carbs again before long.
I say this because that's how this story goes, every time.

 

Thanks! I'll try that, just bought the feeler to check valve clearencees. I'm gonna attempt the zip tie method. (everything is really expencive in Norway, so happy to learn ways to avoid buyng stuff, thanks!)
I'll report back with my findings.

 

I understand your point and thanks for the encouragement. What are the things i would have to buy to do a FULL clean then? I have new float needles and o-rings.

 

IN THE CHURCH OF CLEAN

Follow this tutorial.

 

if your dissassemblings the carbs per instructions above you want to replace all rubber seals.
mixture screw orings
fuel rail orings
throttleshaft seals

 

I have an o-ring kit, I hope I have the right sizes... Throttleshaft seals tho, you guys get them from ebay or are they possible to get in hardware stores?

 

email Len;

info@xj4ever.com

He will have the correct seals for the fuel transfer tubes too (they are not o-rings on the Hitachi's but they may be on the Mikunis).

Cleaning your Mikuni carbs

Replacing your Hitachi throttle shaft seals (same basic procedure as on Mikuni)

Setting the fuel levels

Inside your Carbs

 

with mikuni carbs you have to file down the screws holding on the butterflies they are peened at the factory does not need much filing

 

Now wait a bit here. You've gone from cyl 1 not firing, to being told you need a strip down rebuild of your carbs, including £150 worth of service kit, plus you need to check your valve clearances. It's fixing stuff in case it might need fixing.
I'm not going to say you don't need to check valve clearances, or that your carbs don't need a major overhaul, but you really need to find out why your cylinder isn't firing. And why it took you so long to realize there was something amiss. (Amiss, as in missing, or misfiring).
Anyway, you need to learn to diagnose faults, and then how to fix them.
If you have compression, your valve clearances are close enough (or rather not too tight) to let that cylinder fire. So you can put that job to one side for now. You say you have seen the piston/dashpot whatever lift when the engine is revved up? And anyway, you can inspect the diaphragm easy enoughand also, the diaphragm doesn't do anything on tickover so the cylinder should run even if there was a hole in it (maybe, not checked this).
Anyway, then, you need a spark - did you swap leads and plugs over with no4?
If so and nothing changed then you have no fuel.
Run the bike on centre stand, switch off and drain each carb float bowl into a receptacle, noting how much fuel come out of each - they should be the same. If not you have float level issues. Is there fuel in no1?
If there is, and it's the same- ish as the rest, then you should try a little enrichment - this bypasses the idle jet, so could add fuel enough to light the plug. If not try blipping the throttle open, does this light the pot? If the answer is no to both (I'd be very surprised), then that plug should be wet with fuel, if not, the whole carb is clogged - this is very unlikely, but you never know.
The point of my long and tedious answer is to try to get you to think about diagnosing a problem. Sure, read up and learn how to refurb your bike, the good people here have provided you with that resource, but you have to think about things as well. And then tell everyone what you did.

 

He's gone from a bike that hasn't been refurbished into proper running condition to one that will be in proper running conditon and not need any more work done to it for several years.

In the U.S. carbs and valves are the most neglected parts of a motorcycle, and the carbs on an XJ typically need service every 10 years regardless of mileage.

He already checked for spark, and already bought the most expensive parts for the carb refurb.

 

In the U.S. carbs and valves are the most neglected parts of a motorcycle, and the carbs on an XJ typically need service every 10 years regardless of mileage.

Oh how I try not to be hooked by your nonsense @kmoe, perhaps I'd better not bother with this site...
So American valves or seats are softer than others and actually deform with time?

 

I checked and all float bowls have equal fuel, 1 1/2 shot glass ish. I always work on it with the bike on center stand. Diaphrams didn’t look like they had any hole when I checked. I’ve blipped the throttle, sprayed carb no. 1 with starter fluid while bike running. If the rest of the cylinders rise high in the rpms then header number 1 also gets hot, but no change in sound, and it goes back to low temp really fast. I think it just gets hot from the friction inside the cylinder og the other cylinders make that one super hot..
I don’t see any gas on the spark plug after, and oil doesn’t smell like gas either.

 

do they ship to Norway?

 

E mail Len and ask him.