Help,Losing my mind

[savage454]

I have a 75 with bs38's pods and a 2 into one exhaust open, with a washer welded on to baffle/add back pressure. I've done quite a bit of searching and I think I might have read too many at once.

I'm not sure if the PO re-jetted but the needle does have the clip on the needle one lower than the stock setting (raising the needle). I have them fairly well synced I believe. When I rap the throttle the rpms drop right back down with no hover. My mix screw is at about 1 1/4 turns out. I am still trying to get the mix right.

My problem is One: is seems to run really hot. Like REAL hot. The plugs don't show that I'm either too rich or too lean but I am in the grey color on my left plug and a tan on my right. Two: (and my real problem) When I'm on the highway at about 4500 rpm (65-70mph) it won't go any higher. Giving it more gas doesn't rise it and there is no pull. It is driving me crazy. When I'm on the side roads it seems to pull fine through the gears and pull hard at the power band (3000rpm- 4000) I don't have any popping and there aren't any leaks around my intake that I've found. My valves are set to spec. .002 intake .oo4 exhaust and my cam tension is good.

I've had the carbs off more times than I can remember and are very clean. I did find that on my left carb the thin plastic washer that sits under the clip (it does go under right) of the needle in the slide was missing so I made one out of a plastic the same thickness.

I did find that my clutch was a hard pull and when I adjusted it the PO had turned the screw till it just bottomed (where you would then back off 1/4 turn) and then turned it in about 5 turns So I am working on finding the sweet spot. Like I said it will start to run REAL hot and not want to go into neutral, although it isn't super difficult to find and real easy when cold.

Speaking of cold, when I go to work in the mornings and it's cooler out it runs great (I'm not on the highway though) and then runs rougher when it's hot out on my way home.

Anyways any help would be appreciated.

 

[xjwmx]

On the highway, does the tach keep going up without the bike going faster?

You probably need to check your clutch plates for wear, especially if the po had it adjusted to slip all the time. I checked mine with just a dial calipers.

Adjusting the clutch is simple if it's working. Screw the handlebar adjuster all the way in, bottom the thing on the case cover, back out 1/4 or so and lock it, then use the handlebar adjuster to put the friction zone where you like it.

 

[5twins]

Check your diaphragms for holes. Gently stretch the diaphragm away from the slide and look for small holes where it's attached to the slide. Small holes will allow partial vacuum and slide lift but not full lift. This will usually show up in top gear under load and the bike will only go so fast.

 

[savage454]

Okay 5twins I'll check.

Neither the bike nor the tach will climb.

 

[littlebill31]

If the tach isn't rising then the engine isn't turning any faster. So, you could try a bigger main jet to add more fuel. However, it is a 650 XS and that could be all the gearing you have. Mine would run to 85 and that's it. The throttle could be turned more, but was not allowing anymore fuel into the engine. So I changed to a bigger jet and got some more top end out of it.

 

[savage454]

I was afraid of that. I don't see why it wouldn't just let you throttle it past redline and blow its self to shit. I'll be pretty bummed to know my bike will only do 70mph when everyones claiming 127mph out of theirs. I'd just like to be able to pass on the expressway.

If this bike won't go past 70 it won't see the outside of the garage again.

 

[savage454]

What is one jet size up for the main and pilot for the 75 bs38 carb? I looked on mikes xs and the are only about 70,000 different jets.

 

[littlebill31]

You can do a couple things to increase the top end. Bigger mains will give it more gas, but switching the sprockets will also do this. Switching from a 34 tooth to a 30 tooth rear is very helpful. Then, if it's not enough, get a different front sprocket. You can also get a overdrive 5th gear from Mikesxs. You will always loose to gain though. If you put on bigger sprockets to increase top end, then you will loose some low end torque. I heard a guy complain about wanting better top end so he switched the sprcokets. Now he bitches 'cuz he has no drag racing torque.
And until I see, on video or I'm on it, a XS doing 127 mph, I don't believe it. My bike is quite fast and tops out at 90 with big main jets and 30 tooth rear sprocket. It's a little scary too. I think Pamcopete did a test with the big sprockets and O/D gear and only got to 110.

 

[littlebill31]

They go in 2.5 increments.

 

[5twins]

Stock setting for the needle in the '75 carbs is the #4 slot so it sounds like your needle hasn't been changed (unless you found it in the bottom #5 slot). With your mods and carb set, you may need more than one size up on the mains, maybe 2 or 3. Only testing will tell for sure but eventually you may want to try other sizes in the mid 130s (132.5, 135, 137.5). I doubt you'll need to get up into the 140s. Your Z-6 needle jets will probably limit your main jet size selection and keep it down somewhere in the 130s max.

 

[grizld1]

Savage 454, if "everyone else" is claiming 127 mph out of XS650's, you're hanging with a pack of liars. It takes some serious and competent motor work to get these motors to pull that speed. That having been said, any bone-stock motor in decent condition with stock gearing and competent tuning will take you north of 100 mph (assuming the suspension is also competently serviced).

Digging into the carbies first is a rookie mistake. Set cam chain tension, then set your valves, and be damn sure that cupped valve stems aren't causing your feeler gauges to lie to you: do the adjustment with a dial indicator set up on top of the adjusters. Then check compression, with the motor warm. If it's not close to minimum spec (look it up for yourself in the service manual at www.biker.net ), you have a problem. Then set point gap and check timing with a strobe, checking both retard and full advance timing. If you can't get timing dialed in right at both ends, the bob weights in the ATU are worn. Correct this by replacing the ATU or by peening the tips of the bob weights until they spread to a width of .160" (4 mm.); then reset ignition timing. On your machine there are two sets of points that are timed independently, and at least part of your grief may result from timing being off; the hot side may be running too far advanced.

When you've done all that, address the carbs. Refer to www.amckayltd.com/carbguide.pdf .

BTW, "back pressure" is a sloppy term. The right kind of "back pressure" results from resonant pulses in the exhaust that occur at the right time to enable the engine to develop peak power at the desired rpm, and that rpm is determined by what kind of use you're tuning the motor for. The wrong kind of "back pressure" is simple restriction. A good muffler will give you less of that than the caveman snuffers in your pipe. More noise does not yield more power.

 

[savage454]

BTW, "back pressure" is a sloppy term. The right kind of "back pressure" results from resonant pulses in the exhaust that occur at the right time to enable the engine to develop peak power at the desired rpm, and that rpm is determined by what kind of use you're tuning the motor for. The wrong kind of "back pressure" is simple restriction. A good muffler will give you less of that than the caveman snuffers in your pipe. More noise does not yield more power.

I understand you here, I was just using the words "back pressure" for lack of the correct term. I am really tight budgeted, Like just what I have lying around, budgeted. My wife has a van but with our oldest son, (who's autistic) I can't leave her without a vehicle so this is my daily driver. We both work but every penny we have goes to the boy. It took me literally two weeks to be able to order a new float (which was bad when it arrived, thats another story)I have a 59 Triumph I inhereted, but alas my brother has it.

So anyways I had the washer tacked on there just to reduce noise, I wasn't trying to enhance any performance. I have the valve lash set to spec but with a feeler gauge (all I have) I did this about 4 times for each side until I was happy it was correct. My cam chain tensioner only goes in and out while running about 1 to 2mm.

I am pretty good at following all the directions in the manual but when it comes to timing I can't quite get my head around it. The bike does start right up although I know this isn't indicative of correct timing I think I'm close. I do need to find somebody who knows what they're doing to help me in this respect. The points look to be brand new, as does the ignition advance. One thing I did notice is it doesn't spring back quite like I've seen. As in it doesn't SNAP right back.

I know there is a correct procedure as to what things you adjust before the others and I have tried to follow that to the best of my ability.

About my carbs. They are a mess. The jet? the shaft with small holes the large n8 needle from the slide goes into are both elliptical at the bottom where it looks like somebody tried to take them out with pliers and was unsuccessful. It isn't crushed just slightly out of round. Also the main jet (I think) in the float bowl above the drain has a striped head where the flat tipped screw driver would go. I have cleaned all passages thoroughly and don't want to force that jet out until I can afford new larger sizes. In a few weeks I should probably be able to afford a rebuild kit for the carbs. I will have to do them one at a time though should I wait to do it until I can get both?

One other thing, I looked at my manual and the exploded diagram does not show the flat flexible thin washer that is in the slide that goes (I hope) between the large set needle plate (the hard thick washer with four holes) and the clip on the needle. Is this the correct location for this?

As for the speed, I don't even need it to go 127mph I would just like to have some more pull after 70 (which is pushing it to get it there) when On the expressway to get out of the way if I need to, or for passing purposes. The expressways where I live are full of people with phones attached at their ears and it's like going into battle to get to work. I just need to get out of the way. I would be more than happy to be able to do 80-85 if I need to.

 

[savage454]

I think I will save for the smaller tooth sprocket, This seems like the most economical choice. Like I said I don't need to race, I don't care if I lose some low end torque. I just need some longer legs on the E-way. I would have liked to have had the bike stock but I got a really good deal on it (I got it in a trade) and it was customized this way when I got it. The only thing I added was a long sissy bar to put groceries and shit on it.

Thanks for all your guys' help. I'm sure you're banging you heads at every question that seems to be like the one before it. I have read all the threads I think are related to my problem and have read and printed the carb guide. I guess no two problems are exactly alike even when similar. Anyways I really appreciate the help, it has saved me from just giving up.

 

[5twins]

The exploded parts diagram doesn't show those thin plastic washers under the needle clips because they were not stock. Someone must have stuck that in there, probably to shim the slop out of the needle.

Be aware that we're only dealing with about a 50HP bike here. Gear it too high and it won't pull that gearing to redline in 5th, especially in a state of tune like yours. It won't go faster, it will go slower. In fact, that may be the problem now. It's running so bad, it won't pull in 5th past 70.

 

[shotgunjoe]

Try taking your pods off and go for a run... they may be blocking the air jet like I have read about several times. Just a theory...

 

[savage454]

Thats the thing, it doesn't seem to be running bad at all. It starts right up, it idles fine at 1200rpm, pulls through the gears fine with no stumble or popping I can cruise at 55 at around 3500rpm. Of course I guess I'm notg comparing it to how a properly tuned xs should be running.

I'll try taking the pods off and see what happens. I won't pull in too much crap will I?

 

[savage454]

Also the tube shown here.

is not on my other carb. Is that correct?

 

[5twins]

Yes, that is correct for your carb set. That is the choke feed tube and you only have a choke assembly on one carb. The other carb is fed the rich choke mix through a crossover tube.

 

[littlebill31]

The 650 will not brake any speed records. But having it tuned correctly will really help. Just be sure to get it dialed in before doing any mods. Trying to adjust an engine, that is not at tip-top, for mods will never work.

 

[grizld1]

That tube is the fuel pickup for the enricher (choke). Your carbs use only one enricher valve with the rich mixture carried to the other side by a tube.

You're going to get nowhere until you dial point gaps and ignition timing in correctly--that means with a strobe--and replace the deformed needle jets. Check jet needles for wear as well.