teamtoxic

Hi all,

I've been a lurker here for a while until now, when I hope to make use of the tremendous amount of knowledge culminated on this forum. I recently picked up a Hawk from a friend of mine who, one way or another, ran it without oil. Disassembly showed no damage other than to the crank journal and rod bearings. I replaced the crank (Ebay), all bearings, rings, gaskets.

I have timed the valves according to the manual:
1.) Aligned RT mark with mark on case
2.) Set RE and RI marks on their respective cams flush with the rear cylinder head surface and facing opposite of one another. (This leaves the cam lobes pointing inward and upward towards each other)
3.) Shimmed valves, installed CCT
4.) Rotated crank 1.25 turns CCW to align FT with mark on case and set front cams with FE and FI marks flush with the cylinder head surface. ( This leaves the cam lobes pointing outward and upward away from each other)
5.) Shimmed valves, installed CCT

I have reinstalled everything and am attempting to start, but to no avail. I have good spark and am getting fuel. I performed a compression test and am only seeing 65 psi while the manual specs about 165 psi. I went back to checking for a timing issue, which I think is the culprit, when I made an observation that seems fundamentally incorrect to me:

I placed a rod down the spark plug hole of the rear cylinder to monitor piston and valve location as I rotated the crank. What I noticed was that on the compression stroke, the intake valves are being held open for approximately 1.5 inches from the bottom of the compression stroke. So roughly half of the compression stroke is just pushing volume out the intake, which I think is why I’m only seeing 65 psi compression.

Each camshaft has marks indicating where it should go (i.e. front/rear cylinder, intake/exhaust) and these are in the correct locations. I don’t know the history of the bike all that well so I’m not sure if somebody could have switch gears between camshafts or even if this would make a difference.

This bike has been quite a project for me, as I have sandlasted and repainted EVERYTHING, rebuilt the motor, built a custom subframe and fitted CBR1000RR tail section, wrapped and cut down the exhaust, turned it into a super clean street fighter but have yet to hear it rumble! The goal was to have it ready for Daytona Bike Week, but with less than a week to go it looks like I'll be stuck on my old F4i.

Any help would be appreciated because I’m a bit stumped at the moment. I can’t figure out if I just missed something when I set the timing or if this is a problem with changes somebody else has made before me touching this bike.

Thank you in advance
- Nick

drew_c14

This part is what jumps out at me. The intake valve shouldn't be open for any amount of time if the piston is traveling upward, regardless of which stroke its on.

If I had to make a real quick guess without looking at the book I'd say you are 180 degrees off.

VTRsurfer

Even on a lawn mower engine, but especially on a high performance engine, the intake valve (or valves) opens while the piston is still going up on exhaust stroke and closes AFTER the piston starts up on the compression stroke. Intake will be open for as much as 270 degrees of crankshaft rotation.

Same goes for exhaust. Opens before end of power stroke and closes after beginning of intake stroke.

However 1 1/2 inches is way too much (about 37 mm out of a 66 mm stroke). Recheck your valve timing...do you have a manual? If not, a thread search will probably show the correct procedure.

teamtoxic

I do have a manual and the timing is set per the manual instructions. I used a timing light to verify timing while attempting to start it and saw that the F mark on the flywheel appears in the timing hole with every spark. The F does appear low, almost out of sight, in the timing hole but I can see it. (same for both front a rear cylinders)

When I get back from my trip I'm going to recheck my valve clearances, torque the head bolts a bit more, and check compression again.

Cheers

Hawkrider

Remember, a 4-stroke has two crank revolutions for every 1 power stroke. The cams turn one revolution to every two of the crank. So, it might appear the crank is good but the cams themselves are 180° out. And remember, the spark signal is sensed off the crank, so you might also be sparking on the exhaust stroke vice the compression stroke.

RCVTR

From your description, it sounds like you have done everything right. the spark plugs fire on every crank revolution. You establish which stroke is compression by setting the cams. Front is 1.25 revolutions after rear (or rear is .75 revolutions after front).

Rear cams pointing up and in and front pointing up and out sounds right. I don't believe it matters which cam is which, as far as lobe centers, but be sure you don't have them reversed. They are marked on the cam, between the lobes.

Are you rotating the crank, so the top goes forward? Is the leading side of the timing chain taut, when you are setting the cams? Does the engine spin freely with a socket wrench?

You should not retorque the head. If you torqued it right the first time, it's still right.

HondaJim

The manual actually states if both heads were serviced you set timinig on the front cylinder first, then the rear. I take it you did the reverse?

FL02SupaHawk996

Did you get the same compression reading from both cylinders?

gboezio

Check everything over, maybe it skipped a tooth or two. Re align the crank and sprockets to rule that out. Even with the cams 180° out of phase, the engine will still runs, this bike use a wasted spark ignition system that fires both cyls at every crank turns. Even with both cyls phased 90° from each other it should still fire (but sound funny lol).
Check those valve clearances to make sure the valves don't hang open lowering compression.
No magic here, not enough compression to maintain idle, so you have to go back and check everything. If it all fails try a leakdown test or at least pressurize the cyls, whack the ceramic out of a plug and tap it 1/8 NPT-->grease gun hose--->reducer1/4-1/8 NPT and pressurize the cyl at TDC on power stroke, you will find the leak right away listening, airbox, muffler oil cap, rad cap bubbles. Some rings blowby is normal.

Some upward movement is normal on the intake, SH intake closes 45° of crank ABDC

Truckinduc

The cams have front and rear intake and exhaust stamped on them between lobes.

My rear cam sprockets lined up with the head surface perfect, but the front didnt.

front cyl, not quite TDC, but yes lobes stick up and out


rear cyl, not at TDC either, but close. Lobes inward

teamtoxic

Hawkrider,
Initially I too figured everything was 180 deg off but after checking spark I realized the ignition sparks everytime the piston reaches TDC. This negates that hypothesis.

RCVTR,
Cams are in the correct locations...this is one thing I had checked and then double checked. I am rotating the crankshaft CCW from the flywheel side, pushing the timing chain tought when setting cam position, and yes the engine does spin freely. I did have to remove the heads due to a problem two days after I initially installed them with new gaskets. I reused those "new" gaskets and this is why I was thinking I should torque the heads down a bit more.

FLO2,
yes I am reading 65 psi on both cylinders. This was another thing I found strange.

gboezio,
great suggestion. I was planning a leak down test after confirming valve clearances and retorquing the heads. Thank you for the spec regarding intake closing time ABDC, I will look at this as well.


Thanks everyone for your input, I have confidence that with your guys' suggestions I'll have this bike going in no time.

Cheers

RCVTR

Unfortunately, the head gaskets are torque 'em once and toss 'em.

So where's the problem??

You've crossed it all off the list, but have no compression! sounds like a cam timing issue.

Something's not right.

Hawkrider

Yes, but is it TDC on the compression stroke? Should spark when both valves are shut slightly before TDC.

gboezio

You get two spark per cycle, compression and exhaust strokes, the ICM have no cam sensor so no mean to know the stroke he's on, it's a cheap setup, but still effective.

RCVTR

Typical MC stuff.

I4s fire all four plugs every 180 degress of crank rotation. No distributor and no cam angle sensor.

teamtoxic

Hey Fellas,

so my rebuild was put on the back burner for a short while but I was able to find the issue. For those of you that showed some interest in helping me out, I wanted to give an update, so here it is...

I tore the motor back down again to find the new rings stuck in the grooves on the pistons (both cylinders). In my efforts to start the bike, the rings became seated inside the grooves and I lost all my compression in the process. Yes, I had cleaned the grooves before installing the rings. The only thing that I can figure is that the pistons were warped due to heat when the previous owner ran it without oil (the reason for the rebuild).

I checked the cylinders for roundness and they were close to the service limit so I ordered OS pistons and had the cylinders bored. The engine is now back together and VOILA: 150 psi compression.

I'll be posting pictures of my build soon so keep your eyes peeled. Thanks for all your help

Cheers,
Nick

FL02SupaHawk996

That's great news Nick!
RC