Let me ask the question right up front. What could be wrong with my upgrade?

The guy who wrenches my bike talked me into a 103 upgrade when I went to him for just a cam change. His promise? Increase in the power band, a 50% increase in HP and 40% in torque, all without any real change in mileage. The cylinders and heads were sent for the rework and damaged in shipment. Although the damage was supposedly done during shipment to the shop, the shop replaced them with "fresh pulls" because the damage was not reported in time to make a valid shipping insurance claim. The cylinder was bored and the heads ported. New cams, gaskets, and pistons accompanied the modified heads and cylinders, then re-installed.

Right away I noticed a positive change in the torque range from the cam upgrade (what I asked for to begin with); however, the power was just not there and the mileage sucked royally (as low as 29 mpg vs. the 44 I was getting). My problem is that a post break-in dyno revealed numbers in the stock range w/stage I changes - 74 max hp and 79 torque. If I really baby the ride by not getting over 3,000 rpm or above 55 mph, I can get 37 mpg on a 150 mile ride.

I knew there was a problem when I took the bike back to have a compression and bleed down test done. The mech (I don't consider him a full blown mechanic now, so I just refer to him as "mech") had to borrow a compression gauge and the fitting was the wrong size (automotive vs HD). He could not do the compression test and I'm not sure what he planned for the bleed down. He checked the cam timing which looked okay. The mech wants me to take the bike by another shop to have the tests done at my expense. I don't plan to do that. As a matter of fact, if the mech does not step up to the plate to fix this problem, then I'm probably going to another mechanic and then to small claims court to get back some of what I'm out.

All I want is for my bike to perform at or near expectations. My question is what could be wrong with the upgrade that lends itself to what I described above?

 

You didn't mention any tuner, what tuner are you using? That is probably a big part of your problem, if indeed everything else was put back together correctly. If the compression is there and the cam is installed properly, there's not much left to look at except the tune and there have been many a case of a bad tune being done. I heard of one where a guy took his bike to the dealer, had a Stage 1 done with a tuner added and a dyno tune. He thought it didn't run well, so he had it dynoed at an Indy shop, his HP and torque was less than a stock bike. A short while later with a "GOOD" tune, he was very pleased.

 

The tuner is a PC III usb. Dyno had the air/fuel ratio spot on. I can send you the dyno sheet.

 

his promises were all crap--- hp torque and mileage.

a 103" in any kind of street trim won't increase power by those percentages over stock.

and fuel economy DROPS in a performance motor-- why?

1 larger displacement, more air and fuel per stroke---

2 cams- performance cams use longer duration when both intake and exhaust valves are open, and more lift -- these result in raw fuel exiting the exhaust pipe.


so he may not be the right guy to work on your bike.

what I'd do---?

I'd get it to a reputable tech with good build and tuning experience* and have them go over it, correcting any errors if found.
Is the cam the correct choice for the bike? weight, gearing, comp ratio etc all play into this

If there are blatant errors which fall out side of basic competence, than maybe you have grounds for a small claims against the 1st shop.


* some shops only machine parts but do not assemble or tune--- so they kinda don't know what the application is.
Mike

 

I'll take the mileage hit without complaining, if only I had the power that should go along with it. The shop my mech referred me to for the dyno said I should be getting pretty close to 1 hp per ci with the upgrades - more with a throttle body change.

 

The shop that did the mods also does builds. My mech only does builds.

 

ask the dyno shop for a recommendation to go over the build.

my point re mileage is based on your complaint about mileage----- which is based on his promise.

I point out why mileage is decreased which is basic mechanical function which your mechanic either doesn't understand or didn't explain to the customer.

tuning is an additional variable, but it cannot restore fuel mileage lost to mechanical changes

mike

 

Gotcha Mike, and I agree. I questioned this myself and both the mech and the provider of the mods talked me into it. Getting that behind me, shouldn't I expect a power increase?

 

Unfortunately, there's just not enough information to offer any kind of educated guess on where the problem lies.

The projected increases were reasonable for a cammed, ported 103 vs a stock 96.

A stock TC96 makes something like 65hp and 80 ft lbs, so your projected increase of 50% hp and 40% torque would mean final numbers of around 98hp and 112 ft lbs. That's easily within the reach of a cammed, ported 103, so the promises were certainly within reason.

Keeping the mileage up around stock numbers was a little over-optimistic, though. Pushing more fuel means lower fuel mileage.

 

Take it back and have him make it right.