Just so it is know, Bill and I have very simular motors:
- 1166 kits
- 0.340 Webcams
- 1150 36mm CV's with 147.5 mains
- DJ Needles (Bill setup both sets of carbs)
- 4:1 and 4:2:1 headers
- Pods
- Ported heads
His fried and mine did not as we were doing the near exact same thing on the same ride. The only differences are:
- Bill's L was carrying about about 25-50 lbs more weight (rider plus gear differential)
- Bill had upped his needle 1/2 a notch to lean it out for the higher altitude ridding we were doing at Mt Shasta
- Bill's ported head is not as ported as mine but he has +1.5mm oversize valves v.s my stock 1150 intake valves (+1 mm).
- Bill cams are degreed 110/110 while mine is as recommended 105/107 (We degreed both bikes together)
- Bill has a larger oil cooler than I do
- My oil temp guage never showed I was running hot or anything above about 220-230 degF
- We were cursing through a twisty road at between 15-60 mphs
There really is not much difference beyond that which is scary to me.
Jim, thanks for the comparisons. I wouldn't be too concerned about your bike doing the same thing unless you make some radical change that leads to leaning/overheating. Your oil temp gauge is a fairly good indicator of impending problems. I constantly relied on mine when rallying rotaries, as an early warning tool.
There are some significant differences mentioned above, plus a few that you probable hadn't considered.
1. The difference between a 4-1 and a 4-2-1 system affects scavenging pulses differently, throughout the rev ranges. This means that both your engines would show different AFR's at the same rpms, if you dynoed them together.
2. The degreed differences of the same spec cams along with the different headers can contribute to significant performance/heat variations at certain rpms. Why did Bill not go with Web's recommended degree figures?
3. The differences in porting/valve sizes/seat angles and pocket shape and dimensions combined, are significant when considered as parts of the whole tuning package.
4. On the day, the leaning change of needle position, plus the extra weight Bill's bike was hauling are major contributing differences, especially as you don't know the true CC'c of Bill's combustion chambers.
5. As I recall, Bill also experimented changing the primary air jets on his carbs. Have you done the same, if not, that is another difference.
5. When each engine was assembled, did you have identical deck heights, head gasket thicknesses, squish areas and valve head shrouding relief? Did you both cc your chambers to compare them? How different did they check out?
The one big mistake I see many road bike tuners make is reduce the squish area, at the expense of gaining higher CR with their stock pistons. By doing this, they affect the rate and efficiency of the flame front across the piston crown. To counter this, higher grades of fuel need to be used to stop detonation, or spark advance must be retarded instead. I know that this probably doesn't apply here, but without personally measuring, it's possible to have two engines appearing identical, that DOOOO have significant differences. You do need to establish whether the PO has made an changes to the stock surfaces. This can only be confirmed by exact measurement.
As a matter of interest, what was the difference in compression figures between the 2 engines?
6. At the risk of harping on, altitude changes are one of the many negative side effects experienced by pod tuned road bikes.
