98ci to a 108ci

[Duke]

Anyone have experience going with the 108ci?
I've been working things out with a set of 1700 jugs that were sleeved to the 100mm bore, and a set of JE pistons. I'm using the 1600 heads, modified combustion chambers, with change-over guide pins I had machined. I've been checking everything over and over before I do the full assembly.

[Littlebull]

Are you just going for displacement or are you doing cams to?

[SKWEARpeg]

Davej is running the 108 big bore kit in his bike, and would be a good source for information. He'll probably chime in when he sees this, or send him a PM.

[Ultrastar]

I had a 110 big bore in my Road Star and loved it but I may be wrong but I don't believe the 1700 barrels and the 1600 heads are going to quite work out but it said I could be wrong

[davej]

Mine is a 110 Big Bore. I think Jay is correct but I'm also not positive. I would talk to Nigil Patrick at Patrick Racing to confirm.

[Duke]

Thanks Dave, I talked with Nigel about 6 or 7 years ago, and he mentioned machining new guide pins. How do you like the 110? Do you have any heating problems?

[SKWEARpeg]

I knew it was big. I just forgot how big. Lol

[Duke]

Going for displacement. I'm going to run the stock cams and trying to have a little more torque, keeping the RPMs low. The valves are 3 angel cut and pocket ported, and for now, I'm staying with the stock valve sizes.
The heads should work with the stepped guide pins and running the 100mm gaskets. With all the measurements and inspection I've checked out, I'm hoping that the 1600 heads work. If anyone knows something about this set up, please chime in. Maybe davej will have some information?

[Ftwbear]

Hey Duke. What are the 3 cut-outs along the edge of the combustion chamber for? I would guess helps flow? Or......i see two for the intake and one for exhaust side . I know a stock 1600 doesn't have them.

[Duke]

Help reduce compression and for high swirl during the piston/head quench stroke. Also to help charge the plugs with fresh air/fuel.

[Ftwbear]

Thanks for the response

[davej]

Duke I have the 110 cu in. I had a concern about the heat displacement of the 108 so I went with the sleeved 110. JMO but I think the cyl would be to thin to displace heat. I love the power of the 110. I added cams about a year after the initial Big Bore install. I ported/polished my own heads along with port matching. I also installed Heavy Duty valve springs from Orient Express. They work as good as the expensive (over priced) springs from PR and were only $65 for the set.

[Duke]

Dave, that's good to know, thanks. Is your 110 built from a 1700 or the 1600? The cooling fins on the 1700 are longer and I cut down the sides a little, (approximately 1/4" on the left sides), to match the 1600 heads. I will have to run the 1700 oil lines to clear the jugs.
Do you think the stock cams will work for good torque?

[davej]

mine is built from a 07 1700. The stock cams worked OK but the PR cams really woke it up. Night and day difference and a must even if you don't do them right away. Good thing is they are in a different part of the engine so you really don't have to redo much of anything to install them later. If you do the cams you also will want to get the collapsible push rod tubes.

[Duke]

Thank you, I might just wait on the build until I get the cams. I'm not in a hurry, probably a winter project.

[Duke]

I finally put together the 108ci engine and it works great so far. Definitely more torque and hp, along with good fuel mileage. I’m running the modified stock carburetor and stock ECU for now. I’ll be adding the Dyna 3000 ignition soon. The jugs are the 1700 cylinders that have been sleeved. I had to use stepped guide pins between the heads and cylinders.

[MidnightRide]

I finally put together the 108ci engine and it works great so far. Definitely more torque and hp, along with good fuel mileage. I’m running the modified stock carburetor and stock ECU for now. I’ll be adding the Dyna 3000 ignition soon. The jugs are the 1700 cylinders that have been sleeved. I had to use stepped guide pins between the heads and cylinders.

Are you going to offer up a kit, along with 'An idiot's guide to going 108', at anytime in the near future....? Or better yet, a fully modded motor that can be swapped-out for a core?

The RoadStar 'crate' engine? Might be a fun enterprise!

[Duke]

Hey that’s a thought! I wonder what someone would pay?
I’d probably go broke. Lol

[Duke]

Just called Patrick Racing, and they quoted me a price of $1495. for the 110ci big bore kit. Kit comes with cylinder sleeves, pistons, rings, head gaskets, and machine work to sleeve your jugs.
Patrick Racing said that the prices of everything they get to make up the kits, have gone up tremendously.

[Lug Nut]

Would love to see the torque increase with the stock cams versus aftermarket cams. It's very cool you can maintain good gas mileage and get that extra torque and usable RPM range

[davej]

If I ride normal I can still get in the low 40's mpg.

[HotRod]

The key word being "IF" there Dave

[Duke]

I would like to see the HP and torque figures as well. I wish I had access to a Dyno.

[davej]

On mine
Big Bore stock cam ,self ported heads stock size valves =75hp, 106Tq
Big Bore Self port and stock valves, PR cam= 82hp 109tq
Big Bore PR cam, Pro 1 Racing custom hand ported heads and 2mm oversize valves w/multi angle grind = 94hp, 114tq

Stock 1700 63hp and I think 96TQ
so the increase from stock is pretty nice.

[Duke]

Thanks Dave.
The riding I’ve done with the 108 has been in the high 40 so far, but I can’t keep my right hand from twisting the throttle. I don’t know why, but it puts a smile on my face.
I’m still needing to dial in the tune.

[davej]

LOL twisting the throttle will get me down in the 20's mpg. But sometimes you gotta do what you gotta do. You should consider getting a AFR meter for tuning. If you don't have a fairing to mount it just mount it in a tach bracket or make it a portable tool just for tuning by rigging a sniffer tube to stuff into the tail pipe like they use on a Dyno machine. I found that the afr gauge saved me hundreds of $$ in the long run over dyno tuning. I only had dynos don't after the tuning was done or after mods were made and tuning adjusted.

[Lug Nut]

On mine
Big Bore stock cam ,self ported heads stock size valves =75hp, 106Tq
Big Bore Self port and stock valves, PR cam= 82hp 109tq
Big Bore PR cam, Pro 1 Racing custom hand ported heads and 2mm oversize valves w/multi angle grind = 94hp, 114tq

Stock 1700 63hp and I think 96TQ
so the increase from stock is pretty nice.

The custom porting/bigger valves got 12 hp and 5 tq to the tire OVER your hand porting??? He must know a thing or two...lol. that's impressive gain on a head NOT made for any real high performance with all the other supporting mods!! You have 42 or 45mm carb? Anyone know difference at that level (108/110 with headowrkncams pistons etc) between a stock 40mm Mikuni with big jets and a HSR?

Guy local to me now does 137 cube 1900 motor for Liner/Raider...mintereated to see the numbers that puts down

[davej]

The guy I sent my heads to has been hand porting for over 50 years. He has worked with Nigil from PR also. My hand port was really more of a port cleaning up than a true port job.I knew I was eventually gonna send them for professional porting and didn't want to open anything up to much in the wrong place and screw things up.IMO his hand porting is better than CBC porting because he flows them and makes whatever correction is needed instead of CNC 1 size fits all. All castings are not exactly the same but CNC cuts them as if they were and can leave dead spots in the ports. Google Pro 1 racing heads or "Shortblock Charlie" He has video's online with a lot of explanation of what needs to be done to properly port and flow heads. He does a lot of Harley stuff. When he seen the R* heads he said that it looked like HD used Yamaha design on the M-8 heads.

[HotRod]

I have been stating from the first time I saw an M8 that hd took Roadie heads and put them on their engine. HD cant make anything original anymore!

[davej]

Rod the guy that did my heads is right near you in Tempe AZ

[Duke]

I’ve been thinking about adding a AFR meter. No doubt about it, it would surly help for tuning through out the rpm ranges.

[davej]

Duke you would be amazed at what is really going on the the ranges. The AFR gauge will show it all and is also a great learning tool. I know you would love it.