bought an xj650 desperately need help getting her going

Hello everyone! I recently took a chance on a 1981 seca 650 that "needed the carb rebuilt" I tore them down, cleaned them up and bought the rebuild kit. Got them apart and back together just fine. However it still wont start. It'll start on starter fluid but die quickly after. I ran a compression test with terrible results..... its showing max 60psi and not holding pressure at all throughout all 4 cylinders. Im fairly new to motorcycles I was hoping some one could point me in the right direction here. Any help would be appreciated.
Other details:
11K miles
Carbs don't seem to be sucking up gas
Was filled with at least 5qts of oil when I got it. (didn't start it with all that oil in it)

 

Sounds like an engine teardown may be in order.......60psi is way too low for that engine (should be 145+ psi). You either have:

a) a defective compression gauge
b) bent valves/holes in the pistons
c) a majorly blown head gasket (doubtful)

BTW, the XJ650RJ Seca model was only made in 1982. If you post the first 6 characters of the VIN we can determine for sure what model it is, or you can look here:

http://www.xjbikes.com/forums/index.php?threads/tech-topic-model-id-and-vins.14577/

 

Thanks for the reply! Im 99% sure the compression gauge is good because ive used it successfully on other engines before. It seems I will have to at least pull the head off. which is fine but I cant for the life of me figure out how to get the camshaft chain off. From what I see online ill have to snap the chain?! it just seems crazy to me. Any advice at all id really appreciate.

 

There are four bolts on each of the cam gears. Remove those and the cam caps in order to remove the cams, then the cam gears, then you can pull the head without breaking the chain. Otherwise you will need a chain breaking/riveting tool (and a new chain and master link) as the cam chains are endless.

 

also, im assuming its not holes in pistons because the compression is consistently terrible across all 4 cylinders. (unless they all have equally sized holes in them) and when it say 60psi it peaks at 60 and instantly falls to 0 in about 1.5 - 2 seconds. and that's the same for all 4 cylinders.

 

Genius!! I know the bolts you're talking about, I'll try it out when I get off work this weekend. I definitely want to keep the chain intact if at all possible.

 

You didn't mention checking the valve clearances, which you should do before pulling the head.

 

Ya. Make a chart to write down the clearances. Checking what shims are in there will be really easy once the cams are out. Tighten the bolts 1/4 turn at a time, working crossways on each bearing cap, and from the middle cap toward the outer caps. Bring them down slow and even.

 

ok Ill check the clearances before going any further. I did take the camshaft bearings off (cam covers? im not sure what they're called) and the camshafts moved up a little and now the chain is really tight and it they don't exactly wanna pop back into their seated positions. In other words im gunna have to use the caps/bearings to push them back down into place. does that sound normal? I already loosened up the cam chain tensioner. Also, would bad vales cause loss of compression like this? I really appreciate the responses. Im quickly finding out that Info on these bikes are hard to come by, your advice is invaluable!!

 

Yes, you will use the cam bearing caps to slowly and evenly set the cams back into place.

 

update: so the cam chain is super loose sometimes, to the point where I can almost just pull it off, and then tightens as I turn the motor over. Im assuming that's not normal. Im gunna post some pics momentarily to show you guys what im up against. Also, I haven't done the official rundown yet but just a quick test seems to show even the smallest feeler gauge cannot fit between the valve and the cam lope. ill post my results shortly.

 

look up cam chain tensioner adjustment.

FU

 

You will need to get a very thin shim to swap in for clearance measurements. It sounds like your valves have never been adusted.

I think you would do well to take a break and get yourself a service manual before doing any more work. I had assumed that you already took the cam chain tensioner off since that is typicaly one of the early steps to removing the head from a motorcycle. You can get all of the information you need here, but it's really nice to have that book by your side as you are working.

Also: Really tight valves will not open enough for much air to be drawn in (and compression readings will be lower as a result), but your compression numbers still point to something else being wrong since they are so low.

 

Something is wrong with your compression gauge, it should hold the pressure until you press the release valve. It's bleeding off somewhere.

 

Totally agree. This seems like a bit of rush to tear the motor down. Only 11K and it needs rebuilt, that would have to be some serious abuse. I just did a compression check the other day out of curiosity, and 60 is the number on the first hit, taking about 7 hits on the compression stroke to peak at 150. If the gauge Schrader valve is missing or malfunctioning, you would never get a good result.

Easy to forget also, make sure the throttle is held wide open for the test.

 

The longer the hose on the gauge the more hit's it'll take to pump it up too.

Also, plenty of battery juice to spin it well. Even with a good battery you won't crank an XJ long without discharging to where it affects your numbers. Put on a boost box or jumper cables to a big battery.

 

...AND all the plugs removed so you're not fighting four cylinders. You should also disconnect the TCI or coils so you don't risk damaging a coil.

 

Update: so I'm having doubts about my compression tester. I hooked it up to my jeep and it would bump up to 150 and then fall fairly quickly. So I'm getting a new one for sure. Also the valves read as such
Cyl. 1 int. >.10mm exh. .18mm
Cyl. 2 int. >.10mm exh. .20mm
Cyl. 3 int. >.10mm exh. .20mm
Cyl. 4 int. >.10mm exh. .18mm

These are some pics just to show you what I'm working with

 

Update: so my compression tester was busted. Now I'm getting accurate readings off a brand new one showing 90 - 88 - 91 - 90 across the cylinders. What would cause them to be 40-50 pounds off you think? I think my intake vales need to be adjusted because they're obviously tight.

 

Adjust the valves then recheck. Put a teaspoon of oil in each cylinder and check again. Could be valves not sealing. Could be worn rings or worn bores. Could be a head gasket leak. Could be lucky and it's just a combination of out of spec valve adjustment and stuck rings.

 

Will do!! I'll pull the shims out today and order the correct ones. Also, I noticed when I took my carbs back off and the bowls out that only one had gas in it. The other three were bone dry. Idk if I made a rookie mistake but I think I'm gunna fill the bowls with a little gas before I install them. (I installed and new floater needles durning the rebuild)

 

His valves aren't tight enough to cause it. I'd wet test (teaspoon of oil) next.

 

And I put the floats in upside down. Now that is a rookie mistake no doubt hahaha.

 

She runs!! Also I'm an idiot. But let's move on. Hahaha, so she'll start up nicely cold but after one ride around the block she doesn't want to stay running. And the choke seems to bog it down. I'm thinking rich? It also has a hanging idle.

 

Hanging rpm when I rev it*****

 

Have you synched the carbs?

 

In reference to compression numbers, read this post about the cheap Harbor Freight compression tester. Not sure which one you purchased, but this post gives details on what to look for:

http://www.xjbikes.com/forums/index.php?threads/awesome-low-compression-on-all-4.36719/page-2

 

It seems to me that maybe you haven't completely and properly cleaned the carbs and/or haven't properly wet set the floats or synced the carbs. In addition to the valves--valves first--it's going to take that before it runs well. There really aren't any short-cut to a well running machine--I know from my own experience.

 

no not just yet. I wanna go in order like everyone has been saying starting with the valves. But these last few nice days here in jersey is making it really hard not to just get out there lol. I have to adjust the float levels as well. I read the whole Carb tear down and rebuild on this forum this morning and im excited to put it into practice soon. Im becoming a pro at pulling them on and off already! haha, im also throwing around the idea of having a local guy do it for me. I want the experience but also dont want to screw anything up. Im also getting a whistling whining noise at idle and under load. Is that normal? I took her around the block and she shifted just fine. Im wondering what it is. Some People say its just a classic xj whine but theyre also saying under load. mine happens at idle.

 

I have not set the floats at all. The carbs are coming back off this afternoon. I have a pretty good idea on how to do it i think, lots of reading and youtube videos. hahaha

 

I bough one for 35 bucks at advanced. Ill check it against my jeep today as well. Im kinda glossing over the fact that the compression is so low (which could possibly be a huge problem.) but its that low on all 4 cylinders evenly? (within 2-4 lbs) im gunna put a teaspoon of oil in them tonight and recheck the compression. Im gunna check the compression on my buddies 1986 nighthawk 650 as well with the same gauge. I feel like whoever has it before me would really have had to beat the hell out of this bike to need a new motor at 11k.

 

You will probably do a better job than anyone locally, plus you will be more careful in addition to getting the experience. That was my experience.
I have the whistling or whining somewhere between 2500 and 3500 rpm and I understand that's normal. Someone said it had something to do with the timing chain. If so, I suppose it could be heard at different rpm's based on the chain tension of that bike.

 

Learn to love that whine/whistle. It's part of the Xj. Some people call it " stator whine" or "middle gear whine"... I personally dont care what it is as long as its not the loud death-scream of a speedometer going bad. The whine is distinctive.... It's fun to watch people at carb clinics--- main road, bikes rolling past all day, but every now and then someone will say "sounds like someone else coming".... All heads pop up--- "yup!" Sure enough, a few moments later a bike starts gearing down and pulls up the drive

For carb stuff, if you are onecyo tear into your rack, dont worry.. we're here to helpbyou straighten things out if you get mixed up. if you rather send/take them to soneone who knows what they're doing ....i offer teardown/rebuild service. also, BluesBass is a list member down your way (cherry hill area) ... Talk w/him if you aren't already.

Dave Fox

 

More progress!!! I checked the compression and it's reading 145 across the board!! That's great news. My plug colors are all over the place though. Carbs are coming out, bench sync and fuel float levels are next on the list. Ordering those color read plugs as well. Still having the "starts fine cold then won't stay running while warm" problem. I'm thinking the bowls fill up but then dry up because they are set to low.

 

running good when cold is an indication of a to rich condition. if the float level was too low, it just wouldn't run at all when cold.

FU

 

Update: so I took the carbs back off after reading all the great carb cleaning info on this forum. All my slides pass the "clunk" test now and my butterfly valves have been properly bench synched. also was able to crack loose all four drain screws!! I'm super siked about that. Also, I made a carb stand after I got inspired by a YouTube video. I'm gunna clean the carbs again the right way and then wet set the floats. My colortune plug is ordered as well. Lots of progress today and more to come!! Thanks for all the help so far I feel like I'm almost there!!

 

Again great info and good to know. When I cracked the bowls open again today they were FILLED with gas. Like the second I started to loosen the fourth screw gas came seeping right through the gaskets. I'm assuming that's not normal. I also think I smelt gas in my oil but I might just be paranoid. Either way I'm changing the oil again when I get it running well.

 

yes that is not normal. the float level is a couple millimeters below the top of the float bowl. so you should never have gas running out when removing a float bowl with the carbs level. good idea and cheap insurance to change the oil.

FU

 

Your carbs don't look too bad... Cool carb stand! Now how 'bout a photo of the other side? How is the carb rack mounted on the stand?

 

I'll post a pic from the top and side tomorrow, but it's really simple, just some 2inch to 1.5 inch couplers. Still have a little adjusting to do and I wanna paint it up and make it look nice too. Literally took me 45 mins to make and 15 of that was spent re-wiring my stupid sawsall (old crappy connection finally quit mid project)

 

And only cost 30 bucks if you have the glue already!! Online they run around 80. Obviously nicer and metal and all that but just using my basic setup tonight was awesome!!! So much better then fumbling around with carbs that don't want to stay in one position. And it's a great way to get them perfectly level for the float set I'll be doing tomorrow.

 

Oh and one last thing: I cleaned the carbs fairly well for my first go at it and all the floats were there black normal color. I take the number 4 bowl off today and see this^^^ strange right? It's like white residue on the floats.

 

not cleaned at all. At least not what I would consider cleaned. All the rust there indicates that there is water in your system. I'd HIGHLY recommend draining the tank and thoroughly drying it out, then vacuum it to get rust flakes and powder out. Then fill with fresh gas, and seafoam. Make sure to put a fuel filter in the fuel line, too.

Dave F

 

Did you do anything different to get the good numbers? Just curious since with your new gauge you still had low numbers, but after the short ride the numbers are much improved. Sure is good news though.

 

What EXACTLY did you do for 'cleaning your carbs'? The outsides look real nice. But, the float shown is dirty, the jets are dirty, the chamber itself is dirty, the rail is greasy. Did you replace the fuel rail o-rings or the throttle-shaft seals? How did you bench-sync the carbs?

Sounds to me like on one hand you say you want to do things in order, but on the other hand you say you're itching to ride too much so the 'do it in order' stuff is going out the window. You'll keep running in circles..............

 

I don't think I was clear about "cleaning the carbs" what I meant was I cleaned them before getting on this site and reading the church of clean and I'm definitely gunna go back and do it right however I really don't wanna break the carbs apart. The risk reward factor seems to be to high to break them. However in my defense I am quiet certain all the passages are clean. I can take a high power LED light and clearly look through all of them. I understand the benefits of a perfectly cleaned carb though. And an inline fuel filter is a great idea I'll go pick one up today. And I bench synced the carbs using a needle exactly like this guy here:

 

I put a teaspoon of oil in each cylinder and let it sit for a while. Then she started right up and was able to warm up. The next day it checked the compression and it was 145 on all four. Interesting for sure but I don't want to question it.

 

Honestly I just didn't see the pros of breaking them. They talked a lot about getting them lined up, not snapping butterfly bolts, buying new fuel line seals ect. But why should I take them apart? I just didn't get it.