Topic: Timing with Engine Mods

[MattFreeman]

Please let me know if this belongs in the standard forum.

I have a '76 F1 with:
836
"hot street" cam
increased intake valves
MR port
K&N pods
PamCo ignition and coils

I currently have the timing set so that at full advance the timing indicator mark falls between the factory full advance markers. This means that when I check static timing the "f" is before (in advance of?) the indicator mark on the case.

Is this as good as it gets for this motor?

Ultimately I am trying to figure if the timing has anything to do with the slower than expected top speed (65ish?) or if it is all carb related.

[madmtnmotors]

Wow. Something is definitely out of sorts. My bone stock 750 K8 will carry in excess of the ton without any drama and it's got 60,000 miles. If the problem is carb related I sure hope you're running rich. If you're running lean enough to neuter top speed to 65mph I would think you might be on the verge of melting a piston.

Does it seem to run hot?
If you have chrome pipes, are they turning blue?
What do the plugs look like?

You didn't happen to block off any crankcase vents upon reassembly did you?

[Old Scrambler]

Assuming you have a drop-in cam..............set the timing on the mark..........and let the advancer do its job.  The smart answer to go faster than 65-mph is to shift to 2nd-gear

Check your exhaust.........inside of muffler........and tell us what color is being deposited.  Hope your running 91-octane or better.

[SOHC4 Cafe Racer Fan]

My 836 with ported head, cam and CR29s breaks the ton without breaking a sweat.

[scottly]

  The smart answer to go faster than 65-mph is to shift to 2nd-gear

I was thinking the same thing, Dennis.
Seriously Matt, if the ignition full advance marks are lining up before 3000 RPM, it's not an issue, and even if full advance came in a slightly higher RPM it wouldn't limit top speed to 65 MPH.

[PeWe]

It must be more than one reason of slow top speed here.
Ignition: I got too early full advance with my ignition (First Pamco later Points). No points that can act as a counter force might be one thing. The Pamco rotor spins freely and sloppy advance unit springs will cause full advance way too early. I wrote about it in the forum where I described how I solved it. http://forums.sohc4.net/index.php/topic,131339.msg1464986.html#msg1464986

-I have now OEM points (TEC) with Hondaman ign module. Igntion works fine, F mark at idle, full advance at around 2600-2800 rpms. The mark in case updated with help of a piston stop I used with no camsprocket bolts so valaves do not interfere with the stop.
- The advancer unit has a rather big lash in my engine. I tighten it clockwise lash position, the real mark in case is 2mm to the right in my engine.

- Is the hot street cam properly timed with an adjustable cam sprocket?
Oval holes so the cam timing can be set according to the cam card or 2-3 degrees in advance (IN open 30° instead of specified 28° to get the fun a little bit earlier and less at top rpms). Cam card numbers are usually specified with 0 lash and 0.004" (1mm) lift.
0 lash can be found before measure the total lift by tighten the valve adj screw until the dial indicator just start to move the needle. Lash in valve train will otherwise delay opening valves by several degrees.

[pamcopete]

PeWe,

If the timing goes to full advance early that would not cause this problem because the timing would be at full advance.

Bike goes slow (< 60MPH)

1. Low battery / charging system. A low battery will produce a low ignition voltage at the plugs which is most evident at higher RPM's.
2. Timing. Did you use a timing light to set the timing?
3. Stuck or no advance. When checking the timing with the timing light, did you check for maximum advance at 2,500 RPM.
4. N/A
5. Fouled plugs. Did you install new plugs? Check them after you got it running?
6. Plug wire not making contact in the coil. Measure the resistance from plug cap to plug cap to ensure that both plug wires are making contact in the coil.
7. Brakes dragging.
8. Speedo out of calibration. You are actually going faster than 60 MPH! Use your GPS to check the speedo.
9. Tire pressure. Pump up to 32 PSI for high speed.
10. Drive chain too tight. That will rob you of power to the rear wheel.
11.N/A
12.Choke left on or partially on.
13. Weak or loose advance springs. Weak or loose advance springs cause the advance to use up some of the available movement because you have to essentially retard the advance to get it on the idle advance mark, so there is less movement available at higher RPM's.
14. Timing chain needs adjustment.
15. Cheap or bad gas.
16. Low octane gas.
17. Water in the gas.
18. Partially blocked pet cock or fuel filter.
19. Paper filter that has low flow when the tank is not full.
20. Try a run with a full tank of high octane, fresh, expensive gas.
21. Blocked fuel cap vent.
22. Incorrect sprockets. What RPM are you getting at 60 MPH.
23. Rear tire rubbing on brake rod or swing arm.
24. High wind resistance. Are you a large person?
25. Throttle cable not fully opening the throttles.
26. Blockage in the muffler(s)
27. Dirty or blocked air filters
28. High altitude
29. Very hot air, like 95+F
30. Very cold air, like 32F
31. Low oil
32. Really dirty oil
33. Gas in the oil
34. Cheap pods covering air hole in carb inlet

[MattFreeman]

Wow. Thanks for all the great input so quickly.

First off, 2nd gear? Do I use the foot thingy or the hand thingy to find it? 

Buuutt seriously, let me give you guys a little more background. This has been a almost 5 year project so you may get "best I can remember" alot. This is my first bike in 20 years and the first motor I've ever gotten anywhere near this deep with. Lastly, and I will accept a bit of ridicule on this, I don't have a speedo so I'm guessing on the actual speed  but having 20+ years experience on this stretch of highway I can pretty safely guesstimate that I was doing 60 to 65 mph. And the big thing that will seem stupid is that I did some mixing/matching in regard to the tach and I cannot promise it is accurate.

So alittle about my tachless timing: I had the idle as low as I could manage withthe engine warm to measure static and ran the rpms up till the advance stopped to measure advance.

The engine gets warm but I don't have any base knowledge to say weather it is too hot. The pipes have been sandblasted and painted high temp black so no blueing to be detected. The collector seems a bit sooty.

[MattFreeman]

Here's the plugs. In order, starting with #1

[MattFreeman]

You didn't happen to block off any crankcase vents upon reassembly did you?

I installed a small filter at the valve cover vent and eliminated the crankcase breather and attached the vent directly to the oil tank.

[MattFreeman]

- Is the hot street cam properly timed with an adjustable cam sprocket?
Oval holes so the cam timing can be set according to the cam card or 2-3 degrees in advance (IN open 30° instead of specified 28° to get the fun a little bit earlier and less at top rpms). Cam card numbers are usually specified with 0 lash and 0.004" (1mm) lift.

The new cam didn't come with a card from the manufacturer, I was told to "split the difference".

[madmtnmotors]

As long as it's vented you're fine. The rear crankcase vent is plumbed to the oil tank in the stock configuration and the valve cover is vented to atmosphere (albeit indirectly in stock form) so we can check crankcase vents off the list of potential culprits.

[MattFreeman]

Pete
Great checklist.
I am using a timing light.
Fueling seems good from tank to carbs. Getting same scenario whether tank is full or low. Gas is oil free and of good quality. Is there a way to check for a plugged cap vent?
There's no dragging brake, or otherwise.
Tire pressure good.
Timing chain tension adjusted.
How can I check the advance springs?
I'll count the sprockets tonight.
Muffler is basically open.
Altitude not an issue, I'm in OH.
Battery starts the bike without drama after 10 or so rides/starts.
I'll measure coil resistance tonight.

[Old Scrambler]

Looks like #2 and #4 are fuel-starved and yet the muffler says you are rich. Could be a multitude of sins in the carbs and / or air-intake. Check you plug gaps. Put your battery on the 2-amp charger for a few hours to make sure its at full power.

[PeWe]

About sloppy springs. Fix one of them as I did in my thread. You can also find other threads were this is done.
Hondaman is the MAN giving us good information based on real experiences from back in the days until today.

I have new springs I have not tested yet. From Yamiya750
http://www.yamiya750.com/index.php?main_page=product_info&cPath=246_21_55&products_id=2168

[pamcopete]

Pete
Great checklist.
I am using a timing light.
Fueling seems good from tank to carbs. Getting same scenario whether tank is full or low. Gas is oil free and of good quality. Is there a way to check for a plugged cap vent?
There's no dragging brake, or otherwise.
Tire pressure good.
Timing chain tension adjusted.
How can I check the advance springs?
I'll count the sprockets tonight.
Muffler is basically open.
Altitude not an issue, I'm in OH.
Battery starts the bike without drama after 10 or so rides/starts.
I'll measure coil resistance tonight.

Check that the carb  is completely open when you turn the throttle to wide open. A very common problem. Don't ask me how I know. 

[ivanhoew]

this should be fun when fixed . , those 2  plugs do look lean . can you pull the choke on a little at 60 mph ,to see what happens ?

[MattFreeman]

So I'm getting the impression that baring any spring/advance type issues my timing is pretty good with a bit of advance'd static as long as the advanced/2500rpm setting is correct?

I'll need to find a good day off so I can spend it trying to process all the info in PeWe's thread.

In the meantime we'll be lifting the needles a couple clicks.

[mystic_1]

Have you tried setting the timing back to stock, and seeing how it runs then?

i.e. set the idle timing, not advanced timing, and set it to fire right on the F mark.

Any difference from this, or lack thereof, would be a useful data point.

mystic_1

[PeWe]

And the exhaust is rather open (loud sound), right?
 I got problem during a touring going south many years ago (1:st year engine was tuned 836, head, cam). Bike top speed was around (65mph)130kmh on Autobahn in Germany were I had to drive much faster. I had to remove the baffle and drive very loud to reach normal speed of atleast >180-200kmh. I tried a silent baffle that was way too restrictive. My 4-1 was delivered with 2 baffles, loud and silent (restrictive).

[Haybus]

Have you cleaned and synced the carbs? I'm pretty meticulous about the bench sync, not so much with the vacuum sync. Then adjust the air pilots for best idle. Then do a series of on road tests to determine lean or rich conditions. There's plenty of write ups on these procedures from Sudco, Dynojet and others. Basically you mark the throttle to indicate 1/8, 1/4, 1/2, 3/4 and wot to indicate what circuit is in play when you notice problems. Then do some cruise accelerations in 1st gear starting at 2000 rpm and increase to 3000, hold for 15 seconds, then 4000, hold for 15, then 5000. If you have any surging during this test the needles are likely lean. If you pass the first test, do some medium accelerations in 1st from 2000 rpm to 1/2-3/4 throttle. Again, problems likely indicate lean needles. If you pass the first two, then do a rich test from 2000 to redline with wot. If it burbles or hesitates you're probably too rich on the needles. Of course needle changes on most carbs means starting back at the bench sync and running through all the tests again. Also, if you reach the end of adjustment on the needles you need to change main jet sizes. There's more to it than my simple description. Starting with the main jets in the ballpark helps a lot. If you have noticable problems above 1/2 throttle you might want to try a main jet change since it only takes a few minutes, versus the effort it takes to dig out the needles for the small-ish effect gained.

Alan

[MattFreeman]

Have you tried setting the timing back to stock, and seeing how it runs then?

i.e. set the idle timing, not advanced timing, and set it to fire right on the F mark.

Any difference from this, or lack thereof, would be a useful data point.

mystic_1

I started with the timing set to fire on the F. I haven't run it with the current setting yet.

I will most likely do some more cab tuning first then fiddle with the timing a bit more.

[MattFreeman]

And the exhaust is rather open (loud sound), right?
 I got problem during a touring going south many years ago (1:st year engine was tuned 836, head, cam). Bike top speed was around (65mph)130kmh on Autobahn in Germany were I had to drive much faster. I had to remove the baffle and drive very loud to reach normal speed of atleast >180-200kmh. I tried a silent baffle that was way too restrictive. My 4-1 was delivered with 2 baffles, loud and silent (restrictive).

I used th CycleX "race/street" muffler. It is open. And suitably loud.

[MattFreeman]

Have you cleaned and synced the carbs? I'm pretty meticulous about the bench sync, not so much with the vacuum sync. Then adjust the air pilots for best idle. Then do a series of on road tests to determine lean or rich conditions. There's plenty of write ups on these procedures from Sudco, Dynojet and others. Basically you mark the throttle to indicate 1/8, 1/4, 1/2, 3/4 and wot to indicate what circuit is in play when you notice problems. Then do some cruise accelerations in 1st gear starting at 2000 rpm and increase to 3000, hold for 15 seconds, then 4000, hold for 15, then 5000. If you have any surging during this test the needles are likely lean. If you pass the first test, do some medium accelerations in 1st from 2000 rpm to 1/2-3/4 throttle. Again, problems likely indicate lean needles. If you pass the first two, then do a rich test from 2000 to redline with wot. If it burbles or hesitates you're probably too rich on the needles. Of course needle changes on most carbs means starting back at the bench sync and running through all the tests again. Also, if you reach the end of adjustment on the needles you need to change main jet sizes. There's more to it than my simple description. Starting with the main jets in the ballpark helps a lot. If you have noticable problems above 1/2 throttle you might want to try a main jet change since it only takes a few minutes, versus the effort it takes to dig out the needles for the small-ish effect gained.

Alan

Carbs cleaned (spotless) and vacuum synced. Went from the stock 105 to 135 mains. In a previous thread that main size was suggested along with raising the needle 2 clicks. I haven't gotten systematic abut testing yet but all symptoms seem to suggest that I'm lean. Gonna try lifting the needles then I'll go through some road/throttle tests and I'll report back.

[pamcopete]

MattFreeman,

I guess something that should be mentioned here is that it is impossible to get the proper performance from the stock carbs unless you use the stock air box. The reason is that the stock air box setup has those little velocity stacks attached to the inlet of the carbs and the carbs will not work properly without that setup. I discovered this the hard way after spending weeks trying to get a set of aftermarket pods to do right and others then chimed in in agreement.

So, if you still have the stock air box and velocity stacks, try those with stock jets.