Intermittent Stumble at High Speed Baghira

[chisleu]

What? It's a poly tank
I'm still in the era of steel tanks, didn't realise the Baghira was plastic.

Hehe! Yeah, it's a plastic tank. Honestly, I found the tank to be completely clean. The gas looked great as well.

I think there is another problem. I have no idea what it would be unless somehow the timing is off. I really wish I could use the high performance tools I used on my race car (EGT sensor, knock sensor, fuel injection, wideband, etc)

Seriously considering converting to a fuel injection system.

[Bill Jurgenson]

Probably not getting enuf fuel. The petcock of the MZs is notoriously too small, rtho the Baggi's is a wee bit better. The petcock also has a sieve.
Cup racers drill the petcock out as far as possible. I throw them away and use a Colder quick release connector. For the tank I make a simple straight-thru hose fitting out of brass, soldered. An acquaintance made them from CF tubing (model airplane stuff) and sheet, epoxied together.

Makes everything easier and if you need to shut off the gas, just unplug. And with a hose ID of 8mm it cannot possibly lack, not for that reason anyway.

But it could be that the valves are too tight.
Or the plug gap is too large or the lead has a bad connection. Those screw-on leads are crap anyway.
Or the coil is funky. Doesn't happen very often; I've seen it only two or three time and never with the DENSO coil but who knows.

[chisleu]

Probably not getting enuf fuel. The petcock of the MZs is notoriously too small, rtho the Baggi's is a wee bit better. The petcock also has a sieve.
Cup racers drill the petcock out as far as possible. I throw them away and use a Colder quick release connector. For the tank I make a simple straight-thru hose fitting out of brass, soldered. An acquaintance made them from CF tubing (model airplane stuff) and sheet, epoxied together.

DSC_6970.JPG

Makes everything easier and if you need to shut off the gas, just unplug. And with a hose ID of 8mm it cannot possibly lack, not for that reason anyway.

But it could be that the valves are too tight.
Or the plug gap is too large or the lead has a bad connection. Those screw-on leads are crap anyway.
Or the coil is funky. Doesn't happen very often; I've seen it only two or three time and never with the DENSO coil but who knows.

Thanks for the info. I am certain it's not the petcock. It flowed very well even before I cleaned it. If it used so much fuel that the flow rate was the issue, I would only get ~10m of cruising before running out of gas.

I'm using 3/8" hose because I needed it to make this fuel filter fit.
I checked one of the exhaust valves and it seemed fine. I will check the others before I ride again (I am waiting on a countershaft sprocket nut/washer.)

The plug gap is fine and maybe the lead has a bad connection, but that doesn't explain it acting like it's running out of fuel only when cruising. It can accel from 0 to 70 without issue but it won't hold 70. It could be a coil maybe. if the denso coil is cheapish, I'll get one just for fun.

[DAVID THOMPSON]

look close about getting a good spark

friend said he rode an old bmw for years and thought he had a carb problem....
installed a power dyno .biz 12 volt system
and new spark made the carb problem go away
dave

[chisleu]

look close about getting a good spark

friend said he rode an old bmw for years and thought he had a carb problem....
installed a power dyno .biz 12 volt system
and new spark made the carb problem go away
dave

Good deal. I ripped the boot off of the wire when I tried to remove the boot from the plug originally. When I put them back together it seemed to work ok. I guess I'll replace that wire. The way it looks, It might be easier to replace the entire unit than to get an original MZ part. After the parts I'm waiting on arrive I'll see if I still have an issue.

[DAVID THOMPSON]

old history update
my 1995 saxon tour my 1997 660 mz traveller and my 2002 rt125 all have plastic tanks
wish some one made plastic replacements for bmw 1950 to 1977
my neighbor gets up set when i solder on one of the metal ones in the back yard
he thinks i am going to blow up
but not recommended for those not knowing how
dave

[radiograf]

Dave can I refer you to my previous post in this string about using plastic resin from a fiberglass repair kit. I does work I've done it. Or if you insist on using fire (braze/weld) fill the tank with water, no vapour = no bang!

[radiograf]

The website for power dynamo can be found at http://www.powerdynamo.biz. They don't seem to list anything for the four strokes however

[cat]

Get an NGK racing cable - you can get it on ebay. If you google the site, you'll find some posts about it.

PS: Here you go: http://www.mzriders.com/viewtopic.php?f=3&t=4413&start=0

[chisleu]

nice! Thanks for the info.

After cleaning the tank and filter, and installing the larger fuel line w/ fuel filter, my stumble issues have gone for now. Maybe they won't come back!!

[cat]

So was there any crap on the filter?

[Beefheartz]

had same problem....If the stumble happens at tick over then put a volt/ohm meter on the coil,to test for ignition circuit failure.
|If it happens after acceleration,i.e straight after gear change it is more than likely lack of fuel when re applying throttle,this means filters and or needle jet are sticking or obscured.
Cleaning the fuel filters and tank,stumbling usually happens after fuel level has been low if there is crud in the tank,rain water can get sucked into the tank via the breather pipe if the bike has been left in the rain and specially freezing weather.
If you require an inline fuel line filter,best to get one that is washable and has rubber ring seals.

[chisleu]

So was there any crap on the filter?

If it was, I could not tell. I cleaned it: (simple soap and water, then let it dry, then rinsed with gas before draining and reinstalling)

However at the same time that I cleaned it, I also installed larger fuel hose and an inline fuel filter. It's hard to do without putting a loop in because the bung and carb are so close together, but I was able to pull it off. get the shortest filter possible.

I've never had the problem since.

I did however high-side the bike at 20mph and sever 2 ligaments in my knee. Can't wait to get back on the bike

I'm in SC, USA so I'm missing out on premium riding weather right now