1982 Yamaha Seca 650 (Project)

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I figured as I've posted a few "help" questions and been sort of posting within the "what did you do" thread that I'd make a small thread of the bike I picked up last year and the enjoyment and not so much enjoyment that I've had with the bike.

This is a Canadian version Seca that has 52,000km on it and for the most part runs well and has given me zero issues. When I got the bike it never seemed to quite run right or "steer" right so it became a mission for me to start doing things and fixing and correcting on the bike.

My first course of action was to figure out why it wasn't steering right and I found out pretty quick when I tried to change the brake pads that the right fork tube had a VERY substantial bend in it (https://www.xjbikes.com/forums/threads/front-wheel-brakes-82-xj650r.119773/). Found a great shop in the City I work in with a great mechanic who is capable of working on these bikes and $300 later for machine work, new pads and fork oil the fork tube was straight and the bike tracked better.

This was sort of the end and near the end of the season and I got busy and didn't too much to the bike so it got parked and I started looking towards the other things that needed to be done.

Last month I started to take on the project of finding a good clean airbox with lid and found a guy in town who had one but turned out to be for a 750 not a 650 (https://www.xjbikes.com/forums/threads/airbox-to-carb-boots.124375/) so I had to find another and sourced one up here in the Great North and got it ordered and shipped. Got that installed and one step closer to the bike running better.

Once I got that all sorted it was getting the bike going again and got it started and running but still noticed around 6500-7000rpm the bike would just really stop accelerating and not want to move. So I then moved onto more troubleshooting and that is when I found out the bike was using resistor plugs and caps so the next order of business was to get that ordered and sorted. Unfortunately no shop in town stocks the original style plugs and they all want to sell you the resistor type so online I went to trusty Fortnine and ordered proper plugs and caps and now awaiting for that to arrive.

As an FYI cap #1 measured out at 7.9ohms and the rest were within normal spec.

I then moved to the small oil leak at the front of the bike and decided it was time to source an oil cooler for the bike and luckily I found another GREAT shop up here in the Great North and was able to order the cooler and adapter and get that coming to me and once that arrives I will install.

I also took a look at the coils and measured those out and found while the primaries on both were on the very upper end of spec the secondaries were still quite reasonable, so I'll be keeping an eye on those and if need to I'll either replace or get Dyna coils.

I'll be moving onto doing a valve check here in the next day or two and seeing where those are.

 

I'm from Canuckistan as well, Mississauga (for now)and once I get my maxim 1100 all up to snuff, my 650 seca will be the next project bike. It was my first bike, so it holds a special place for me. I'll be following your progress. Where abouts is local for you? I've ordered from xj4ever for the hard to find stuff or the value of one-stop shopping, it would be great to find somewhere up here for the odds and ends.

 

Most of my parts come from sourcing locally from the shops, ebay or a new one I found in Ontario called Hoop Rider. Not sure how long they have been around but its where I found my airbox and oil cooler setup from and their prices are pretty reasonable.

I've looked at xj4ever for stuff but unfortunately with the crappy exchange rate and crazy shipping rates it has me looking for alternative sources. As an example I need to replace my drain bowl screws and I'd like to order the allan head versions but after the exchange and shipping I can just make them for a few dollars in my garage.

 

Well changes the plugs and decided to change mixture screws to 3 turns and now it's breaking up around 5,000 rpm.

Can too little or too much fuel cause this breaking up?

I plan to check valves in the next couple of days and look into doing a sync too.

 

Yes, fueling can cause that. So can several other things.

Have valve clearances been checked?

Idle mixture won't affect fueling at 5,000 RPM significantly, and 3 turns out is only a tiny bit rich.

Have the carbs been broken down and properly serviced?

Despit changing the plugs to non-resistor there could be an ignition issue. Have you cecked the reisitances of the coils, and removed the spark plug caps from the wires to check for corrosion?

 

Coils were checked and both primary and secondary are in spec

Caps and plugs are brand new as of today

As I said valves will be checked in the next couple of days

Haven't even looked at the carbs gets, but I have read a few things that I will try when it breaks up.

 

90% of running issues are due to carbs that have not been to church.
99% are due to people (not you) who swear that they already cleaned the carbs and everything is fine on that end.

IN THE CHURCH OF CLEAN

 

Oh I am doing my best to not get into the carbs. Seeing that I will have a challenge just getting the float bowl screws out lol.

 

There really is no option if you want it to run right. If the float bowl screws are stuck that's a sure sign that the carbs have never been touched.

 

Oh.. they have been touched... and touched... and touched.. and they look like the carcass of a dead bird after a few wolves had lunch.

 

I meant properly. Like a prom date.

 

So raining out so not much riding happening tonight.. but did a couple quick things. I upped the spark plug gap from .025 to .028 as per a finding on Chacals site.

While I had the plugs out I figured I'd do a compression check...

#1 = 100 psi
#2 = 90 psi
#3 = 90 psi
#4 = 100psi

Now I know that valve clearance plays a role in this and being that I need to do that still.. My concern is that will it be a realistic thought I can gain 28 psi for #1 and #4 and gain 38 psi for #2 and #3? As 128 psi is the minimum for these engines...

This bike also has like 55,000km (Canadian) on it.. so... yeah.

Thoughts?

 

First thought is make sure your compression gauge reads true.
Second thought is to make sure tht you account for local altitued (if needed).
Third thought is to make sure that you are following the specified procedure (throttle held open, engine cold).

Valve clearances do play a significant role in compression readings. Keep in mind that when an engine sits for an extended period of time there will be at least two cylinders with one valve open. That allows moisture to accumulate, eventually washing some of the oil away from the compression rings. It's common for engines that have sat to have rings that are a bit sticky, or slightly corroded. Usually runing the engine for a good while will free things up and compression will improve. Your numbers (if accurate) are not so low that you should be concerned at this time.


Your bike has low miles.

 

K-moe has never been to prom with Matti.

 

Did a clearance check today.. And based off the spec sheet of 0.004-0.006 on the intake and 0.006-0.008 on the exhaust here is where I sit...

#1 - Ex: 0.006 / In: 0.005

#2 - Ex: 0.006 / In: 0.005

#3 - Ex: 0.007 / In: 0.004

#4 - Ex: 0.006 / In: 0.004

While the majority are on the tighter end of the spectrum it looks like for this season at least I would leave the valves alone. Next season though.. well probably time to do some shims...

 

Sometimes its the small victories to offset the ugly ones

Was able to find a OEM seat/helmet lock with key.

 

Any carb cleaning/ setting may be a moot point until you check your valve clearances.

 

Read my posts lol. I posted the numbers.

 

Somehow I missed the post while looking at the thread on my phone, carry on. I am following your progress.

Looking forward to it,

 

Alright got the bike out tonight for some testing.

Bike still breaks up around 6,000rpm and just does not pull through. Tried adding some choke, switching to prime and res and nothing changes.

Thinking TCI

Noticed also and it didn't do this when the pods were on the bike that it will idle high up to 3000-4000rpm when at a light.

I know it needs a carb sync and its running lean because of this so time to see where air leaks maybe.

 

don't go down that road
if it acted better with pods and breaks up with a air box the jets might be setup for pods, so now your running rich. take the filter out of the box and see what it does. the idle goes high because it needs a running sync
but if you're not going to go through the carbs completely you might as well go watch cartoons

 

Carbs are next.

What I haven't made note of yet in this is that the breakup I'm experiencing happened when the pods were on the bike. That behavior has not changed. And this is now after I've changed to new plugs and caps and confirmed healthy coils.

What has mostly changed is the hanging idle.

Carbs are coming off this weekend to give them a look over to see if anything has been changed.

 

Ok .. pulled carbs this weekend and dove into them and here is what I found..

The top needle? Didn't think these bikes had needle adjustments? Also the washer I know is an old trick as a spacer but on a bike with an adjustable needle?

The top jets are 50/205 but it seems stock should be closer to 50/195? Assume the 205 is making it run a bit richer.

With the bottom though this is where things are weird... I see the #43 marking which for Canada is normal, but I'm not seeing markings on the other too?

Thoughts?

Top - Needle


Top - Jets - 50/205


Bottom - The only one with a marking says #43 which is stock for this bike

 

That is an aftermarket jet needle.
The air jets are the correct size, and in the correct positons.
The main jet is probably aftermarket too. Do you have a set of jet drills, or wire gauges?

 

Yeah got no tools for that.. will see what I can find. I know of the jet drills.. .but wire gauges?

 

Jet gauge tool. It's a set of precision-gauged wires for measuring jet sizes.
The name escaped me earlier. The closer it gets to move day the more things I have to remember. Moving sucks.

 

So I found a set of numbered drill bits and it seems like a #56 fits into the main jet which from what I can see falls into a 120 jet size.

Being that its a 120 jet that means its +10 over the stock number which means its running a whole lot richer than it originally was lol.

So far carb wise even though pods were put onto it not much was changed except for the main jet.

Should note.. I am running a UNI filter so I don't think the 120 main will be a problem.

Also figure I'll drop the needle a spot or two and see if that helps fatten it up a bit.

 

So going over the carbs I have discovered that 3 of the 4 cinch rings for the rubber diaphragms are broken.

Anyone know if this is an issue or nothing to worry about. Could it cause a air leak?

 

split is not an issue

http://xjbikes.wikidot.com/carb-specs

 

Here is a picture.. Its not like just a split.. they are full on missing a good chunk. When I pushing the slides up and down in the bores 1,3,4 and sounded like a whoopie cushion going pffft where #2 did not.

https://i.imgur.com/8FFIFWm.jpg

 

that could be from someone removing them you have to split them .normal

 

So got the proper TCI for the bike (just cause) and also got some proper clamps for the air box boots.

Figured since I have adjustable needles on this bike I'd experiment with them but unfortunately I think I went the wrong way. I initially thought dropping the needle (richen) would help but it seems that maybe since I have a 120 main jet over the 110 that I think is stock I think I need to lean this bike out.

I have an order of new float bowl screws showing up tomorrow so I'll rip out the carbs and lean out the needles and see if that helps.

I remember why I hate carbs so much

 

Dropping the needle (raising the clip) leans the mix out.

 

Yeah I'm running into the bogging down low now.. around the 3-4k range where before it was in the 5-6k range.

From all the reading I've done this signifies a rich mixture and I have the screw at 2.5 turns out right now.

So I want to see if I might be able to get the slides out without pulling the carbs and if not.. well out they come again!

 

look at the hole in the bottom of the slide, does it look original?

 

Yeah slides are original.. Needle is different as I'm thinking someone tried to change it out for when they were running pods.

So I discovered you CAN remove the slides with the carbs still installed so I pulled them out tonight and move the clip up a few spots and now at idle when you try to accelerate it goes POP POP out the exhaust so this is now a sign of being lean.

I went to hook up my aux tank so I could play around with the adjustment screws but I apparently used the hose for something and so will need to pick up some before I go adjusting the air screws.

 

the slide would be original but some of the jet kits that were for running pods came with adjustable needles and a drill bit to enlarge that hole in the bottom of the slide
once that's done everything changes

 

are you still running 50 and 205 air jets? 50 and 195 are stock



50 and 205 are for maxim 650


changing needle height does not affect the pilot jet circuit

 

Hrm... Maybe I'll pick up the used carb set I found and then can do some comparisions.

Yeah just trying to get this thing running with what I have first

Also adjusting the needle has made a difference in how the idle to 1/4 throttle responds.

 

is your bike a Canadian bike or US bike?

 

100% Canadian so I know the jetting is a bit different.

 

Years & Models: 1980-1 XJ650 Maxim, Midnight Maxim, and XJ650RJ and RJC Seca Canadian models
Carb Manufacturer: Hitachi
Carb Series: HSC32
Carb Model ID: 4H800
Main FUEL Jet Size: #110
Pilot FUEL Jet Size: #40
Main AIR Jet Size: #50
Pilot AIR Jet Size: #195
AIR COMPENSATOR Jet Size: #36
Starter FUEL Jet Size: #40 (non-replaceable, in float bowl)
Main jet NEEDLE ID: #Y-12
Main needle JET Size: #3.2mm (the main needle JET is also known as the "power valve" or "emulsion tube").
Fuel Level in float bowls: 3mm +/- 1mm (.118" +/- .039")
Idle RPM's: 1,050 rpms

its running. you may want to install correct air jet

 

So forgive me as I'm trying to learn what all these jets do... and perhaps the air jet is causing my issue now.

So last night I moved up the clip to lean out the bike and today I set the screws to 2.5 turns out but it didn't seem right. I then moved them to 3 and it was getting better then I moved them just a bit past 3 of maybe 1/8 turn and the bike no longer stumbles at low rpms and has a SMALL stumble around 6500-7000 and can work through it then rev to 8,000 without issue.

I'm going to adjust the screws out a bit more to see if I can clear that up and if I can assume then as we are figuring that the pilot jet needs to be lowered.

Correct in this thinking?

 

pilot air jet is oversized and at 43 so is the pilot jet. you will only want to change 1 thing at a time.

 

So I'll probably just buy that carb bank to have a spare set on hand and original parts.

With that said after turning out the screw a bit more and went for a ride I noticed a few things:
a) Popping on decel
b) 1/8 to about 1/4 throttle good response
c) Anything after about 1/4 throttle and cracking the throttle bogs down
d) The throttle response on this thing now is absolute nuts and just wants to go lol

I'm thinking I'll drop the needle down and see how it runs from there and order the carbs and get those jets looked at.

But I'm pretty damn happy with where it is right now compared to where it was.

 

air jets work backwards from fuel jets, bigger air jets run leaner

 

+1 And you're already running lean. Popping on decel is the clue on that assessment.
You need the correct main air jet at a minimum.

And again, dropping the main jet needle leans the mixture, which is the opposite of what you need to be doing. That bog is a lean bog, not a rich bog.

 

read this over
http://www.factorypro.com/tech/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

 

Good to know and makes sense.

Yeah, wasn't sure which way to go so I apparently went the wrong way I'll drop it down again and adjust from there.

Tough to know what to do when you feel like your starting from scratch, but now I feel like I have a fairly good baseline

Thanks will look it over.

Also just ordered those carbs.

Even through these trials and tribulations and not really being able to ride the bike at all this year... the short jaunt tonight with how it is now running better than last year put a substantial smile on my face.

 

Well decided to drop the needle clip down 1 and well the bike just runs like crap again. Before I did it at least it would go and actually want to go.. but now.. blah.

So I think I'm done farting around until I get that other set of carbs and start changing out the air and main jets and if need be ... the needles.