help loss of power at low rmp and high rmp power jumps

ok guys im new to this site. i just finished my xj650 and everything is good but i went for a ride this morning (1st time) and noticed the power wasnt there the more i ride it got better but it sounds like im going 100 mph but im only going 20mph. when i gun it the power starts to come back and then pow it kicks in. the bike has been sitting for some time. what do you guys think? 82 xj650

 

is it misfiring on the low rpms?

my problem was the tci ignitor box. ran good enough around town but when it hit 4k rpms. then all was good.

when i first got the bike. it was pretty gutless. untill it hit 4k. then it was like a supercharged turbo. virtually had noooooooooo accelleration in first gear.

 

that fixed the problem, when you pluged the new tci box what happen?

 

the bike ran like it was supposed too with replacement tci. put the old box back in. ran like crap again.

 

Solo, what does it mean that you just finished your 650? You mention that everything was good, does that mean the bike ran correctly for some time before the issues began? Please clearify if (1st time) means first ride after overhaul or first ride of the day. Off the cuff, I'd say you need to clean the carbs, but that is based on an assumption. The TCI is also another possible culprit as Snowwy pointed out.
Snowwy, if the bike still ran with the old box (albeit poorly), your symptoms are a classic indication of bad capacitors (they change value over time). You can swap them out yourself if you want to rescue the old one as a spare. It's not hard and the parts run about 7~15 dollars.

 

I choped the crap out of the bike but didnt do anything to the motor. I hear these bike are fast but i have a xj 750 and a xj 650 that are doing the same thing. so is it the tci box? i dont want to rebuild the topend if i dont have to. this bike was given to me as a trade for building a bike for someone.

 

i sold the yamaha, it's what virtually paid for the suzuki. as the suzuki hadn't ran for 10 years. PO couldn't figure out what was wrong and after 10 years practically gave the bike away.

wished i kept the yamaha so my boy could go riding next year. but it was the only way i could afford the suzuki at that particular time.

that thing had 2 IC's. aren't they what controls the timing. i took electronics in high school LONG time ago. i though IC's were basicaly what controled the thing. as far as any type of programming goes. all the other stuff were just stuff to make the thing run.

 

If it "Sounds like" ... you're going a 100 MPH ... but, ... in reality the Bike is actually going quite slow ...

That would make me think that what you are trying to describe to us is that your CLUTCH is slipping.

1) Try to ADJUST the Clutch ... (see LINK below in my Signature)

2) DO NOT Slip the Clutch or Damage to Steel Clutch plates will happen.

If this turns-out to be a Clutch issue.
Get a Manual.
Replacing an XJ-Clutch is a job any Hot-Rod Guy can do in a few hours IF you have the Illustrations and Play-by-play offered in the Workshop Manual.

(( Season ending sales are starting. Complete Clutch Kits are on sale. Check with out Parts Man, here, for COMPLETE Clutch replacement items.))

 

If by "that thing" you are referring to the Suzuki, I wouldn't know. The XJ uses a single TCI box that has a single Integrated Circuit chip with the spark advance curve burned into it. The TCI takes the pickup coil input signal (pulled off of the end of the crankshaft) and uses that signal to initiate the ignition coil firing. It is nothing more than a slightly smarter than dumb switch. It is by today's standards a relic.

 

the yamaha tci is what i was talking about. the suzuki only needed a battery from sitting for 10 years and the plug wire fixed is what the PO couldn't figure out.

front cylinder wasn't firing. the PO thought it was starving for gas so i gets to straighten out his mess now that winter is almost here. i put the stock jets back in and the throttle needles back to position. just gotta fix the one cylinder not wanting to idle like it should and stop popping.

i've been riding suzi for 2 months now. no problems other then the idle. have to hold the throttle SLIGHTLY.

 

So, nothing radical like cleaning the carbs and synchronizing them, or adjusting the valves, or anything like that? Oil and filter change?

You can't simply ignore a 25+ year old motor and wait for stuff to go wrong; it will.

From your description it could be a slipping clutch, ignition problems, carb issues or a myriad of other things. We need more info:

Miles on motor?
Intake mods?
Exhaust mods?

 

That's what I got out of it too...

 

Carbs are clean and the bike idle smooth.
motor has no knocking.
i adjusted the clutch and no diff to the power.
check plugs and wiring seem to be good.
when for another ride and when i ease on the throttle it seem to pick up speed better, but when i gun it no power until i get to High RMPs then it picks up speed. now the question is it the clutch or the TCI? by the way guys thanks.

 

I give up.

 

Miles on motor? 22,000
Intake mods? stock carbs
Exhaust mods straight pips

Dont Give up!

 

Winner!

Let's tell him what he's won.....

You now get to change your main fuel jets and/or shim your needles.

The straight exhaust will cause a lean condition.

What do your plugs look like?

White I'd bet.

Show us a Pic of the end of the plugs.

The fix is simple. First make sure your carbs are 1000% clean. The emulsion tube should be removed and verified clean. If dirty, clean, replace on bike and try again.

Next go get some 4mm flat washers. Remove carb hats, slide out piston, remove needle drop washer between needle and brass slide. Ride bike again. Good? Done.

Not good? add another washer or order some jets.

I ended up +2 main jets and 1 shim on my 650 going froma 4-1 to a 4-2 no cross over and big harley mufflers.

 

his story sounds like he revs the throttle but the bike don't gain speed unless the rpms are up.

i'm with rick. slipping clutch.

 

Did you change the handle bars? When I changed mine to smaller handlebars there was a lot of extra clutch cable and I had to adjust the cable quite a bit because the clutch was slipping and doing what you have described.

 

iwingameover- wow im a winner sounds like I won a lot of carb work lol.

ok guys in pulled out the plugs and you are right white. (your good) I also checked the compression and 120 psi on all. I will adjust the clutch and take it out for a ride today. I will also clean the carbs AGAIN :cry: . thanks guy i will keep you updated.

 

I like the bike. Looks good.

120psi is low. Did you have the throttle open all the way? Have you checked your valves lately? Try a teaspoon of oil in the cylinder and see if those compression numbers come up. If the numbers come up a lot with the oil then it's bad/worn rings. You won't get top performance out of it at 120psi.

 

i add oil and it was the same, but I didn't have the throttle open. I really haven't did anything to the motor. I have build 3 xj but all i do is the fab work not the motor. i guess this is a good time to start. the funny thing is the motor sounds real good and strong. what sould I start with? carbs? clutch? valves? tci?

 

Stock CARBS but not a stock airbox, is it? Pods and straight pipes will require carb tuning/rejetting.

In order?

Valves: checked and adjusted as necessary.

Carbs: Surgically clean; pass the "clunk" test; float levels verified using fuel and the clear tube method; bench sync'ed; then a running vac sync--

THEN and only then you start your rejetting project...

Clutch? Get it adjusted correctly and if it still slips then it's teardown, clean and inspect/diagnose time. Doesn't matter what order you do it in.

TCI only requires attention if it actually has a problem. Be sure to unplug it prior to compression testing, so it won't damage itself trying to fire plugs that aren't there/aren't grounded.

 

Redo compression test with throttles open.

Then follow fitz's list.

 

Iwingameover, I completely agree with you on all your points and you are right to throw the validity of the test up to inspection as the correct method of testing is paramount to a good diagnosis. I will however throw in my opinion about the following minor details.

I will agree but it isn't by much. The major concern is how the 120 is spread out across the bank of cylinders. IF they are all 120, I'd say it'll be fine (with appropriate regular servicing) for years yet. I've seen more than a few 4 bangers (including the XJ engines) run just fine at 120 psi.

You are 100% right of course. But if this bike is to be a daily rider/commuter, I don't see where this is a problem. If the fuel economy is normal (approximately 42~45 mpg range-ish), I wouldn't ring any alarm bells. I'd only worry if the bike was to be raced/dragged where tip-top performance is a must. Now, it could be said that by the nature of the bike in the photo, odds are pretty good it will see some action so a re-ring job wouldn't be a bad idea.
I look forward to hearing back from the owner after another test (as recommended).

 

If you are riding along slow and turn the throttle to make the bike go faster ...

and, the BIKE don't go faster, ... but the ENGINE do go faster ... this means

the clutch is no good. Clutch slipping.

 

i like that 42-25 mpg rating.

congress wants cars to get better mileage but they screwed the crap out of our bikes.

the xj's originally got 60+ back in there day. i was talking to a lady just the other day. she has a yamaha 400 special. 2 cylinders. top end rebuilt. and she gets the same 45 mileage my suzuki 1400 gets. those 400's got close to 70 back in there day.

anyone getting worse mileage in there cars? i haven't had a full tank in 2 years so i wouldn't know.

 

I was looking at the new Royal Enfields...they are 500cc singles, wish they had a twin. Beautiful bikes.



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Surprisingly, they all come with fuel injection now, surprising because their emphasis was always on retro. 85 mpg! I like that...

My '83 XJ650 has always impressed me...solid 55 mpg if ridden right, I've squeezed 60 out of it. Very predictable that it will start sputtering and need to go to reserve at 110 miles, and take exactly 2 gallons to fill. Even with a tankful burned out totally assclowning, it'll still get 45 mpg or so...

 

I have another xj650 motor that i was going to build a frame around but maybe i will pull out the clutch and put it in this bike. what do you guys think about getting a clutch from ebay, what should i look for.

 

It comes from the ethanol. It's less efficient so you get less miles.

Same with ULSD less efficient, less miles.

Maybe they pollute less per gallon but you use more of it.....

Way off topic.

 

I've purchased clutch parts off ebay and have gotten a mixed bag. One fellow referred to his clutch pack as "near new" with blued drive plates (the steel ones) and maybe 0.002 over minimums on the friction plates. The inconsiderate jerk even said he would replace them and never did. Another sold "used but in good shape" with effectively the same result.
Best bet is buying new from a known source and I'll plug our resident parts expert, Chacal. For about $75 you get a new set of plates and springs. Peace of mind if you ask me.

 

Agreed. Buying pre-owned clutch parts (other than for the basket or hub) is like buying pre-owned brake shoes.

If your plain plates aren't warped or burnt blue, all you'll need are friction plates and springs. (And a new gasket.)

 

The easiest job would be to replace only the Clutch.
Not to change the whole Engine.

You can have complete Brand New Clutch --- $95.00

 

Here's more pix of the bike.

 

Do you have car shocks on the rear end?

 

No the shocks are the stock ones just painted. after i replace the clutch im going to sell it if anyone is intersted. thanks guys for all the help im going to replace everything tomorrow night and friday.

 

How much fuel does that tank hold?

 

about 3 gallons. it has a small tunnel.

 

ok guys i adjusted the clutch and went for a ride and now it runs like a bat out of hell. thanks guys. one last question the charging system wont charge, what is the most common thing that goes out in these bikes; like the xs650 the rotor goes out al lot on those bikes. thanks guys.

 

Alternator brushes mostly. Check them out and replace as needed. 10mm is minimum service length.

 

I just wanted to say thanks to everyone that helped me. The bike runs awesome. This site kick ass.

thanks
solo