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PostPosted: December 23, 2016, 9:33 am 
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If you continue down the two stroke road you my want to look into a spark plug clearer. I found it ten times easier to read a clean plug. I would try to shot for an 1/8" carbon ring at the base of the plug. Typical start a little rich [cooler mornings] and work down to the lean and mean ratio by the afternoon. For the initail setting of the timing use a dial indicator to set the piston, then verify the timing flywheel marker line to the casing notch is correct. Then check to see if using a timing light give you the same results. If there is a difference then adjust it so you can do a quick timing light verification if ever needed. Don't waste your time and money on warm up plugs. You will be changing plugs so often, there is not any advantage. Dave W


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PostPosted: December 23, 2016, 12:20 pm 
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Dave
I'm going to be hitting you up for some more info when I get back home. I was able to verify TDC with the dot and notch before we packed up Wednesday afternoon. I was just starting to check initial timing on #1 when Wifey Dearest came to the garage and dais "Let's Go! Change of plans, we're picking up Baby Girl in Charlotte."

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PostPosted: December 28, 2016, 11:13 am 
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OK, so I have the carbs apart for cleaning and rejetting.
Current setup is
Pilot 035
Main AB300
Starter circuit jet 135

HELP!!!!!

I'm not sure where to go to get her to start on a cooler day.
I think I need to bump up the pilot to 040

not sure what to do after that

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PostPosted: December 28, 2016, 10:12 pm 
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Looking through the goodies I have a wide assortment of mains, zero pilot or start circuit jets.
Looks like I need to do a little internet shopping.

Anyway while I had them apart I swapped the mains for 340's per the manual for this elevation.

Put it all back together and battery was too low. I got it to turn over a few times, but not fire. Put the charger on for a bit and she started. Seemed to be running on 2 instead of all 3. I shut it off after a few seconds and will try again in the morning after the battery has a full charge.

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PostPosted: December 29, 2016, 12:32 am 
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The manual may not be correct for your elevation because your chambers may be different than what it used to have. Just something to keep in mind. You're sort of in an area where the manual haas good advice, but you don't know what camshaft is in the motor.

What relation is an AB300 to a 340 jet? The letters don't mean anything to me. Is the 340 4 sizes larger than the 300? Are you competing at the altitude your living at and what altitude is that ( roughly )?

A pile of main jets and no pilots or starters might be saying something - but you could probably take it either way :rofl:

If you're trying to fix the starting maybe the starting jets are where to begin, but I don't know.

The two places I'm starting from here are 1 that you have a good running engine that has been competing successfully and 2 that cold starting is low on the list of your priorities to compete successfully.

Can you start the car from outside standing next to it, just reaching into the start button on the dash? That's a help. It's not like a car with a carb where you can push the gas pedal and the accelerator jets pump fuel into it to prime. I hope I'm not stating the obvious to you, but lots of folks these days have never driven a carb.

What does the primer circuit you mentioned do?

I choke my formula car with my hand, that won't work with your triple carbs, but perhaps a scrap of 2x4 would cover the mouths and you could try choking that way.

Does your bodywork make the carbs inaccessible? I didn't run the rear body work on my car and this is one of the reasons. You may need it to be competitive though...

I understand more why you are getting into the carbs instead of hand priming or hand choking if you can't get to this stuff in real life this spring at an event. I've never needed to do this after the first start of the day though. It usually seems to come from letting the car sit outside overnight while I camp at a track.

Sorry for all the questions...

I don't think you want to change something like a pilot jet for cold days and a cold motor. The motor will be hot when it's running and it will mostly be hotter out too. The pilot jet may also go up a ways into part throttle, like %25. Your lucky on this because mostly you don't care about half assed throttle settings, your going to have RPMs and plenty of throttle most of the time... Still you don't want the plugs fouling while you are staging and it would be great if it warmed up with out fouling...

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PostPosted: December 29, 2016, 8:45 am 
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The Mikuni's that I worked on alway had an enrichment piston on the side of each carb. You have to adjust [Sync] the cables so each of the carb 's enrich circuit to open for starting.
Make sure you have the sealing rubber cap on the enrichment cable ends. If missing it allows some air into the circuit. And then there is always starter fluid :mrgreen:
Dave W


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PostPosted: December 29, 2016, 9:19 am 
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horizenjob wrote:
The manual may not be correct for your elevation because your chambers may be different than what it used to have. Just something to keep in mind. You're sort of in an area where the manual has good advice, but you don't know what camshaft is in the motor.
yep, I know nothing about what's been done on the inside, just working from a chart in the manual and adjusting for elevation

What relation is an AB300 to a 340 jet? The letters don't mean anything to me. Is the 340 4 sizes larger than the 300? Are you competing at the altitude your living at and what altitude is that ( roughly )?
300 to 340 is 4 sizes larger. Car is moving from roughly 3000 feet to sea level.

A pile of main jets and no pilots or starters might be saying something - but you could probably take it either way :rofl:
yep. Chad didn't have any problems starting in warmer weather. he bought an assortment of mains to get dialed in moving the car from FL to TN

If you're trying to fix the starting maybe the starting jets are where to begin, but I don't know.
Today I'm going back to the books to better understand the enricher circuit. It should start with a really rich condition easier than one that's too lean.

The two places I'm starting from here are 1 that you have a good running engine that has been competing successfully and 2 that cold starting is low on the list of your priorities to compete successfully.
It's actually pretty high on my list. We start running in February. The temp could be 30 or 70. Since I'm running a total loss system, I need her to start quickly and easily from cold. I had an issue with the F500 last year with not having enough battery left at the end of the day to get it to fire for my 4th and 5th runs. Don't want a repeat of that if I can avoid it.

Can you start the car from outside standing next to it, just reaching into the start button on the dash? That's a help. It's not like a car with a carb where you can push the gas pedal and the accelerator jets pump fuel into it to prime. I hope I'm not stating the obvious to you, but lots of folks these days have never driven a carb.
I can. It's a bit of a stretch, so I've been thinking about adding a second start button close to the engine bay

What does the primer circuit you mentioned do?
After much reading I finally found the answer to that one. The Start circuit has a plunger that lifts a valve off the seat, letting engine vacuum draw fuel through the start circuit jet. Air comes via one of the drilled holes. As far as I can tell there isn't an air or fuel adjustment screw for the start circuit. it seems the adjustment is how much slack there is in the cable of the 3 position lever. (off, half, full)

I choke my formula car with my hand, that won't work with your triple carbs, but perhaps a scrap of 2x4 would cover the mouths and you could try choking that way.
more likely a 1/4x4 its a tight space between carb face and final drive housing. Not even enough space in current setup to run an air cleaner or air box. I'm working on that part mentally right now. trying to figure a way to fit a shallow box or move the final drive back an inch or more.

Does your bodywork make the carbs inaccessible? I didn't run the rear body work on my car and this is one of the reasons. You may need it to be competitive though...
It does. Body is easy on off though. body is also likely to get a mod to make easier access to the engine bay.

I understand more why you are getting into the carbs instead of hand priming or hand choking if you can't get to this stuff in real life this spring at an event. I've never needed to do this after the first start of the day though. It usually seems to come from letting the car sit outside overnight while I camp at a track.

Sorry for all the questions...

I don't think you want to change something like a pilot jet for cold days and a cold motor. The motor will be hot when it's running and it will mostly be hotter out too. The pilot jet may also go up a ways into part throttle, like %25. Your lucky on this because mostly you don't care about half assed throttle settings, your going to have RPMs and plenty of throttle most of the time... Still you don't want the plugs fouling while you are staging and it would be great if it warmed up with out fouling...

Yep, I think I need to concentrate efforts today on the start circuit and see if I can get it dialed in. Pilot will only change if I can't get it to idle properly in the 1 to 3 turns out range after it's warmed up. Mains I'll start out rich with the 340s and see where EGTs go on wide open throttle and what the plugs look like

Got to get the beast to start first so I can fine tune it.

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OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216


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PostPosted: December 29, 2016, 9:22 am 
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davew wrote:
The Mikuni's that I worked on alway had an enrichment piston on the side of each carb. You have to adjust [Sync] the cables so each of the carb 's enrich circuit to open for starting.
Make sure you have the sealing rubber cap on the enrichment cable ends. If missing it allows some air into the circuit. And then there is always starter fluid :mrgreen:
Dave W


Thanks Dave. This is a triple carb TM38 rack. the enrichment runs from a single cable and a linkage bar connects the 3 carbs.
Having some coffee and doing a bit more reading this morning before heading to the garage.

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OOPS I did it again
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PostPosted: December 29, 2016, 10:56 am 
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Mind you I've rebuilt or opened up and gone over Mikuni carbs dozens of times. That was all in the 70's and 80's though.

Remember the advice from Bent Wrench above, that to get the engine vacuum to the starter circuit you need the throttles closed the first turn or two of the crank. I'm all for getting this stuff to work, you don't want to kill that starter motor. I was able to use a trickle charger to keep my ford battery topped up, that won't work in parking lots. So look into ways to charge it from your car. You can also use the car battery for starting. You have probably seen the welding equipment socket you can fit to your Amod and use with custom jumper cables. If your battery is not top shape, then the voltage drops while starting and you don't get a good spark.

The comment about the camshaft was actually referring to your expansion chambers. For a 2 stroke the intake and the exhaust are very important.

I used to carry jets for hillclimbs to adapt to altitude change, but never used them. SO don't have suggestions, sounds like the factory manual is helpful, but 4 sizes seems a lot of adjustment. That sort of implies 6 or more sizes to get to Denver. Tht would take you from not running hardly at all to running really well - it's a lot of change. Just needle height can make a noticeable change.

Something that may help is that when you go for the cold start crank it about 2 turns and then stop and wait a little while for fuel to evaporate in the crank. Maybe wait for 30 seconds or 1 minute.

Is it older fuel you are using, maybe winter blend would start easier for you. The light components of the fuel may have evaporated. So newer gas. Also maybe try the oil squirt can trick you can open the slides put a quick squirt across the carbs and then close the slides - give a few seconds and try the start. If it's good enough for F1 (70's - 80's )it may work for you too.

I agree you want this to work, going to event and dealing with this crap and wearing out the starter etc. is just the wrong place for your head to be.

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PostPosted: December 29, 2016, 11:27 am 
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Just wanted to add that the expansion chambers shouldn't really throw off the starting circuit stuff, they would have way more effect when the engine is running at large throttle and high RPM. Plus the motor from a snowmobile should have a pretty strong starter circuit anyway. So exploring that seems like the best path. Plugged/dirty jets, air leaks, loose cables etc.

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PostPosted: December 29, 2016, 9:08 pm 
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So I hit the garage after coffee this morning and thought about priorities Spark, Fuel, Air. Got to have all three to be happy, but don't nuttin happen without spark.
I pulled the plugs, cleaned and gapped them.
Next up check the static timing again and be sure there's a spark cranking over by hand.
OK got spark :thmbsup:

Fuel and air - decide to trust the start circuit to do what it should after I cleaned everything yesterday.

I put the plug in, set enrich to full, and push the starter.
whirr whirr whirr COUGH
again whirr whirr whirr COUGH
set enrich to 1/2 Whirr whirr VROOOOOM
followed by spit, sputter cough cough cough cough vroom cough cough croom cough
You get the idea, running but not great.
Set enrich to off push the starter
vroom cough vroom cough vroom cough vroom cough

shut it down pulled the plugs 1 was firing 2 were wet

ran the fuel screws in all the way and backed off 1 1/2 turns
install plugs push starter
vroom vroom cough vroom vroom cough
pull plugs 2 firing 1 wet

I chased it the rest of the day and I can't consistently get #2 to fire. It'll run briefly after cleaning the plug then foul out again.

I thought it may be the mag triggers for the MSD box, so I checked the magnet to sensor gap over 100 thousandths, too high for my taste. I cut shims for behind the sensors and got the gap to 50 thou

Still not firing on all 3. Not sure what to do next.
I think I'll swap trigger wires between coil 2 and coil 3, then move spark plug wires from 2 to 3. If the dead hole moves from 2 to 3 I have a coil problem.

I don't really think it's the coil as it will light off for a little bit before it fouls.

honestly, I think there may be a big puddle of oil in the crankcase that's screwing things up. I'm getting way more oily goo coming out the exhaust than I've ever seen on a healthy 2 stroke.

At least it made noise today.

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OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216


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PostPosted: December 30, 2016, 6:50 pm 
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Update from today. I was in and out of the garage as we had a lunch date with the kids that ran rather long. I got a couple of hours in before lunch and about 3 after lunch and still chasing #2 misfire problems.

Doing a little more research last night I learned that sometimes fouling plugs can be corrected by closing the spark plug gap. A few top racers run gaps in the 18 to 22 thou range. I had them gapped per the manual at 28, so pulled the plug, cleaned them, gapped to 22
fired it up and it was at least idling on all 3.

I let it warm up and started running up the revs
I had dropped the 300 jets back in yesterday and with them in it would lean out and shut off at WOT.
I threw in the 320s, could run at WOT but not above 5000 rpm
I threw in 340s and it was bogging at WOT seemed to rich
I threw in 330s still bogging at 4500 to 5000 rpm

Car running in the garage at 5k is absolutely deafening. Even with ear plugs its crazy loud

I probably had it running about 30 minutes total and burned a gallon of gas. Seems a bit much, but I don't have anything to go on.

When I brought it back down to idle #2 cylinder was dead again. plug was cool, exhaust pipe was cool, so it had died prior to WOT run.
:BH:

I'm feeling more and more like it's not healthy inside the motor.
With the block good and warm after a few WOT pulls I ran a compression check and got 65 to 70 across all three cylinders....
Pretty sure it needs a new top end.

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OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216


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PostPosted: December 31, 2016, 11:39 am 
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You will never see high compression numbers on a 2 stroke. Theoretical compression numbers do not account for closing the exhaust port half way up the cylinder. Do you have chrome on aluminum bores? They need to be check with hot cylinders. It sounds way to rich. You need check AFR under actual road load, [ a clean chop at WOT ] or you are just running on the needle. I would start by lowering the needle 2 notches then go for the main jet reading. Dave W


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PostPosted: December 31, 2016, 5:57 pm 
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The stuff I've been reading online seems like I should see 100 psi or more on a healthy motor. I haven't done it yet, but I need to pull the heads off and look at the pistons and cylinders. I did the compression test with it as warm as I could get it with it running poorly. EGT was up in the 750 degree range. Water temp at 200 with good flow through the radiators and the car not moving, just a box fan blowing some air over the rad and the exhaust out of the garage.

I took a bad fall on Christmas day and landed flat on my back on the sidewalk. A trip to the ER said nothing broken, but I've been hurting like hell all week. Last night before dinner I felt a really sharp pain in my back. I couldn't sleep last night and was barely able to get out of bed this morning.

I hobbled out to the garage for about an hour and started pulling the exhaust, draining coolant pulling the carbs. Basically getting ready to tear down the top end. Wifey Dearest and Baby Girl came back from shopping and I asked WD to take me to Doc in a Box, I couldn't take the pain any more.

Get to Doc in a Box and Doc says he wants a full series of X Rays and gives me a shot of drugs. 20 minutes later he comes in and tells me I have clean breaks on #7, 8, and 9 on the right side about 4 inches from my spine. Tells me I'm going to hurt like hell for the next 6 weeks and gives me a script for pain meds.

Now I'm on the couch in a semi-recline with a good dose of drugs and a heating pad. Hopefully I've be able to deal with the pain enough tomorrow to pull the heads and reeds.

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OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216


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PostPosted: January 1, 2017, 11:54 am 
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That does not sound like fun! They just tape up the ribs, and then hand you meds :(
The 100 psi sound right. You go thru rings pretty quickly on a racing two stroke. I had single ring pistons and chance them every 300 miles, and new piston crank assembly very 600 miles. Dave W


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