Now that I am testing the 88 K100 I'm finding I have a miss when I try to go 30mph for more than a few seconds and at 40 as well.Right around 2500 RPM with the throttle just cracked off idle position. Any ideas ? Everything is new from the fuel pump to but not including the injectors. At speed she runs like a champ . A bad wire? Spark plug? injector? The gas is new and everything is working as it should .

You need to do a plug chop, run the bike at the speed that the bike is missing. Then while running at this speed and at the same time, pull the clutch in and kill the engine. Doing both at the same time can be a bit tricky and it might require a few runs to get it right. Find yourself a nice quiet road with a safe area you can push the bike onto to remove your plugs. With the plugs removed you should be able to read which plug is missing. As well as the ones you listed it could also be an air leak check all the rubber bits for leaks using a propane bottle or carby cleaner. Have you checked your valve clearances or done a compression test.
Regards Martin.

I was thinking it was lean.It acts just like one of my two strokes acts when it's too lean.The bike bucks at that rpm.I'll try a plug chop.I did give it all new o rings on the injectors when I put it all back together. Next dry day I'll get out and do this.  Thanks for your opinion,I really value the input I get here. Ed

yamaguzzi wrote:Now that I am testing the 88 K100 I'm finding I have a miss when I try to go 30mph for more than a few seconds and at 40 as well.Right around 2500 RPM with the throttle just cracked off idle position. Any ideas ?

In which gear are you going 35 or 40 at 2500rpm when this miss occurs? Is it an intermittent miss with long intervals, or rapid fire? Is it surging, too?

On the 2v Bricks there is a built in self test feature that is often overlooked. With the bike idling at 1000 Rpm press the green starter button. If the mixture is correct the revs will stay the same or rise very slightly. If the revs drop or rise significantly the mixture is incorrect. The adjustment is on the top RH front corner of the air box under a removable rubber plug and requires the insertion of a 5mm allen key to adjust it. You can either use an exhaust gas analyzer or the Lean Drop Method which can be looked up, plenty of posts on how to do it. I bought myself a Gunson exhaust gas analyzer about 18 years ago and it has served me well. If you do get one treat it with care it does not like being dropped or abused.
Regards Martin.

MartinW wrote:I bought myself a Gunson exhaust gas analyzer about 18 years ago If you do get one treat it with care it does not like being dropped or abused.

I'd just shift to a lower gear. Gunson abuse is too tempting. How do you control that urge, Martin?

Laitch wrote:

yamaguzzi wrote:Now that I am testing the 88 K100 I'm finding I have a miss when I try to go 30mph for more than a few seconds and at 40 as well.Right around 2500 RPM with the throttle just cracked off idle position. Any ideas ?

In which gear are you going 35 or 40 at 2500rpm when this miss occurs? Is it an intermittent miss with long intervals, or rapid fire? Is it surging, too?

Usually 3rd or 4th gear is the worst. It makes the bike buck and as soon as I increase the throttle it smooths out until I back off again and just have the throttle just slightly off idle position

I resist Gunson abuse by going to EAA meetings. So far I've been clean for twenty years, be strong brother and take the righteous path.
Regards a reformed sinner.

yamaguzzi wrote:Usually 3rd or 4th gear is the worst. It makes the bike buck and as soon as I increase the throttle it smooths out until I back off again and just have the throttle just slightly off idle position

I didn't read in your previous posts that you've checked the valve clearances then balanced the throttle bodies. Yours has low mileage so the valve clearances might not be an issue but the balancing and lean drop procedures could improve overall performance. Consider putting that on the schedule if it hasn't been done.

My bike likes revs. I think 35 is too slow in fourth gear, especially in traffic where quick acceleration is useful for self-preservation. Try running in lower gears at higher speeds in that range for a while and break in the bike some more. It needs to limber up.

I would first check your spark plugs. I posted a while ago about how to test them with a DMM. A forum Search should find the post.

yamaguzzi wrote:Now that I am testing the 88 K100 I'm finding I have a miss when I try to go 30mph for more than a few seconds and at 40 as well.Right around 2500 RPM with the throttle just cracked off idle position. Any ideas ? Everything is new from the fuel pump to but not including the injectors. At speed she runs like a champ . A bad wire? Spark plug? injector? The gas is new and everything is working as it should .

My first thought was that it's lean probably from an air leak and it's not hard to get a leak when all those bits that were rubbery and flexible have gone hard with age. The next check is plug leads.

So,this morning I pulled the plugs just to see where they are at.They are all pure white ! This bike is running way too lean.So now I'm asking how can I enrich the mixture easily to see if it cures this problem ?

If all four are lean then something affecting the mixture as in fuel supply is probably the cause.


I wonder is it possible inside the tank there is an issue with one of the fuel pipe connections causing low fuel pressure? Or an issue with the fuel pressure regulator. Or as happened somewhere else on the forum one of the fuel lines connected wrong way round?

Throttle position sensor creating an issue? Actually that did cause an issue of lack of fuel on my K100 2v at one point and a clever friend picked that one up.

You didn't do the injectors but all being equal its not likely to be the problem. Could a bad earth anywhere interfere with the signal to the injectors?

Here is a video of the miss .It happens right around 1300-1400 RPM and sounds like a lose wire or something .It's very puzzling . You can hear it closer to the end of the video.It is throttle related but I'm clueless as to where to look for the cause. I'm an old school carb guy with vintage stuff. This high tech stuff is a mystery to me. I couldn't seem to post the video right here in this reply so I hosted it on my blog .  It's real short just 10 sec or so but you can hear it and see where it happens on the tack .Here is the link
https://motoguzzi850t.blogspot.com/2017/10/engin-miss-video.html

Check for air leaks at the vacuum port caps, the throttle bodies and the breather hose. What happens when you press the starter button while idling at 1000 rpm?
Regards Martin.

MartinW wrote:Check for air leaks at the vacuum port caps, the throttle bodies and the breather hose. What happens when you press the starter button while idling at 1000 rpm?
Regards Martin.

I haven't tried that yet ,I will do that tomorrow morning when I go out fresh.

92KK 84WW Olaf wrote:If all four are lean then something affecting the mixture as in fuel supply is probably the cause.


I wonder is it possible inside the tank there is an issue with one of the fuel pipe connections causing low fuel pressure? Or an issue with the fuel pressure regulator. Or as happened somewhere else on the forum one of the fuel lines connected wrong way round?

Throttle position sensor creating an issue? Actually that did cause an issue of lack of fuel on my K100 2v at one point and a clever friend picked that one up.

You didn't do the injectors but all being equal its not likely to be the problem. Could a bad earth anywhere interfere with the signal to the injectors?

The pressure regulator is new,so is everything in the tank and all the hose from the tank to the motor.The clamps are all new and correct for FI ,I double checked every connection inside the tank and outside before putting the bike back together and putting fuel in the tank .So tomorrow I pull the bike apart and look at everything again closely,run it and see if I can locate an air leak with propane. It's making me crazy !

For all 4 to be lean like that the problem has to be at the plennum or further back to the filter. Is the Z shaped engine breather OK and is the filler plug at the crank cover sealing. Haven't seen it done for some time but it was a big joke to make that plug lose and they would run like shit and get the owner really upset at his new K playing up with much amusement to the onlookers.

I press the starter button when the motor is turning 1000rpm and it raises to about 1100 .I found corrosion on the contacts for the throttle stop switch so I cleaned it with contact cleaner and put it back together with dilectric grease did the computer as well .So now when the rain stops I'll take it out for a test ride.

Supposed to rain here all week, it's been raining since last Saturday, so while it's raining it's a good time to check for air leaks.
Regards Martin.

I spent a few hours on her today.I found corrosion on the plug to the throttle sensor so I cleaned it with contact cleaner I did the starter button test and it went up by about 100 rpm.I checked for leaks,I cut the end off the vac hose that goes to the injector bar so it is tight ,did the same for the vent hose under the tank with that valve on it then I ran her.It stopped raining and I went for it.The bike runs way better now ! It's actually drivable.No more bucking. I went about 60 miles and she's pretty good now.While on the road while stopped at a traffic light I brought the rpm to 1000 and did the starter  test again and there was no up or down movement in engine speed.I did this a couple times during the ride with the same results.I think with a little more attention to the vac connections and an adjustment on the throttle switch it will be 100% Right now I'd say it's at about 90 to 95 %. The fuel light came on after 120 miles . I zeroed the counter last fill. It took 3.8 us gallons giving me 31 or so mpg Is that all these get or can I expect better with more tuning ? I'm getting real happy about this bike the more I ride it.So far I have put on around 175 miles and in that short time she's getting sorted out pretty well. Thanks for all the help guys !

You have funny size gallons in US but over here I use a rule of thumb of 10 miles to a litre when calculating trips and fuel stops, roughly equivalent to 45 miles per uk gallon. That has worked on the K00LT, the K100RT and is now working on the K1100.

I think your 31 miles per US gallon is working out under 39 miles per UK gallon so you have some room to improve.

However some of that may have been you just going through making sure its right.

I didn't read back in the thread to see if you had done the injectors but the plugs suggest they are fairly consistent. Mine were fairly poor and only three ended up good. You may gain something by doing them but make sure you have replacement seals [8] and a few spares.

  Always good to see a positive outcome.
Regards Martin.

MartinW wrote:  Always good to see a positive outcome.
Regards Martin.

Yes it is Martin but it couldn't happen like this without all the help we all give each other. Without this forum I'd be struggling with this thing.Eventually I'd get it but with this forum it was actually fun to overcome these problems .Thanks again to all who helped me figure this out. The next major piece of work on this bike will be brakes and tires  in a couple months when I get the money saved up to get the parts.I want to use steel braided hose ,rebuild both front and back master cylinders, the calipers are fine so they will just get new pads.With any luck I'll be traveling to someplace nice next summer on this machine.

The forum is great and its always good to see someone get a problem solved.

We do get to meet up sometimes and in fairness to all there are some great guys on the forum.

Fixing things can be fun.

Nice to see you reopening the thorny subject of tyres........

YG  Point Seven Five I and  as well as a few others are running a Chinese rear M/Cyl there is a link to various ways. 
http://www.motobrick.com/index.php/topic,9364.msg79956.html#msg79956
And seeing as you are changing the lines and this is required with some of the Brick conversions you might want to have a look. My master cylinder cost me the huge amount of $13.33 Au I bought three one for spare wouldn't even bother trying to put a kit in it for the price, and one for a mate.  A better boot cost me $4.00 Au I got a deal on the hose but it should retail for $60.00 Au. Conversion was done in March 2017 and has a slightly firmer feel to the pedal, but I have no concerns at all with the conversion.
Regards Martin.

Yes, I have to credit Young Engineer for the idea of the Chinese Master Cylinder.  Mine works so good I had completely forgot about it until Martin just mentioned it.  There is a thread at MotoBrick.com someplace where we discuss our retrofits.

About mileage, you may have a faulty engine coolant sensor or a dirty connector that is causing the engine to run rich.  It could also be that you burned a lot of gas testing things.  Run a couple more tanks to see what you get.  Put some Techron Injector cleaner in as well.  You should be getting between 45 and 48 mpg with normal driving around town with your bike.  High speed sport riding or munching miles on the Interstate will lower it to around 40 mpg.

Point-Seven-five wrote:....
About mileage, you may have a faulty engine coolant sensor or a dirty connector that is causing the engine to run rich.  It could also be that you burned a lot of gas testing things.  Run a couple more tanks to see what you get.  Put some Techron Injector cleaner in as well.  You should be getting between 45 and 48 mpg with normal driving around town with your bike.  High speed sport riding or munching miles on the Interstate will lower it to around 40 mpg.

I'd agree with this. My K100 's and K1100 get 5.0 to 5.5 lit/100km which converts to about 42 to 47 US mpg. However, I've always found if I ride a little harder I get better fuel consumption probably because the machine is operating more in the power band and therefore more efficient. If you cruise around at about 3 to 4k rpm in 4th or 5th, while you have torque, there's little power performance and you'll use more fuel.

When I pulled the coolant sensor on the K100RT it was thickly covered in crud and am fairly sure was not getting a correct reading. I had a new one so I put it in rather than messing around with testing etc but am fairly sure a good clean up of the sensor and the contacts may well improve things. There was an improvement after wards.

Thanks guys,I'll have a look at the coolant sensor this weekend when I will be fooling around some more with this bike.I'm of the opinion that I should ride it some and run a couple tanks of gas with injector cleaner added before I do anything else now that I have it in driving condition just to let it work itself out some. I did have the cleaner in the first tank of gas but now it's got a full tank of pure gas so I 'll add some before I go out and burn this tank.It feels like the more I run it the better it runs so we'll see . Where are those " Chinese " master cylinders sold ?

yamaguzzi wrote: Where are those " Chinese " master cylinders sold ?

There is information about purchase sites at the beginning of the thread linked in Post #26 of this thread. That thread—at Motobrick.com—has installation information, too.

yamaguzzi wrote:Thanks guys,I'll have a look at the coolant sensor this weekend.
....

There's a simple testing procedure outlined about 2/3 the way down the Trouble Shooting page. The link is on the Portal tab.

It's been a week since I started riding this wonderful motorcycle.After fixing the miss I rode her lots all week and by the end of the week I was on the high way with her doing sustained speeds of 70 mph for an hour. The more I rode her the better she ran ! I started using regular unleaded 87 octane gas and the motor seems to actually like it. It starts right up when cold or hot and is smooth running. So now that I know I have a good motorcycle I'm going to buy her some new tires . It's been a great experience getting to know this motorcycle.She's totally different from my other older bikes.

Sounds like early symptoms of the onset of the dreaded Kpox!

good work yg

yamaguzzi wrote:After fixing the miss I rode her lots all week and by the end of the week I was on the high way with her doing sustained speeds of 70 mph for an hour.

What fixed "the miss"? Was it just cleaning the throttle position sensor contacts, running it more, coolant temperature sensor contact cleaning, a combination of those or something else? I can't quite nail it down from what you've written.

Leaving the brakes until last definitely shows dedication to thrill though.

Laitch wrote:

yamaguzzi wrote:After fixing the miss I rode her lots all week and by the end of the week I was on the high way with her doing sustained speeds of 70 mph for an hour.

What fixed "the miss"? Was it just cleaning the throttle position sensor contacts, running it more, coolant temperature sensor contact cleaning, a combination of those or something else? I can't quite nail it down from what you've written.

Leaving the brakes until last definitely shows dedication to thrill though.

Actually I made the brakes work before I did any other work on the bike .What I did was take the masters apart and clean out the crud then flushed and bleed them with new fluid. This being said they still need to be gone thru properly. I bought master cylinder rebuild kits and I want to put on steel braided hoses and new pads before I really start riding this bike . The way they are now is fine for the testing that I'm doing. I put on around 700 miles in the past two weeks.At first it was rough but ok and I took your advise and decided to run it in.I found some corrosion on the wires to the throttle stop switch and took care of that and at the same time cut a half inch off the vacuum lines at the connections to get a tight fit.These two things made the low speed miss go away.After I burned off the tank of high octane gas with injector cleaner added I started filling it with regular 87 octane  .There was a noticeable improvement it the way she ran after one tank .Then I got bold and took her on the interstate yesterday and did 165 miles at 65-70 mph. The gas mileage increased from 31 MPG to 46 MPG .She ran great and now the testing is over.She's a keeper and I am now willing to spend money on the tires and brake upgrades as well as a new rear shock.I am very happy with this bike and the more I ride her the more I like her but I won't be riding her now until I get the new rubber and do the brake work.I pushed my luck as far as I'm comfortable with and I have 5 other bikes I can ride so. Your advice was very useful and I thank you. Perhaps we will meet up on the road next summer when I'm taking the long way thru New England up to my camp in the Adirondacks on her first real long distance ride.